A Europe Without Internal Frontiers: Challenging the Reintroduction of Border Controls in the Schengen Area in the Light of Union Citizenship

Abstract Border controls within the Schengen area are meant to be a thing of the past. Yet, since the refugee crisis of 2015, “temporary” border controls have become quasi permanent in several European Union Member States. Although these controls are against the letter and spirit of the Schengen Borders Code, the Commission has not taken any measures to enforce these rules. One of the reasons for the dismal state of the Schengen area is the one-sided focus on the abolition of internal border controls as primarily functional for the establishment of the internal market. This comes at the expense of Union citizens’ rights and disregards the fundamental role that the abolition of border controls has on how citizens see the Union in political terms and conceive themselves as Union citizens. Against this background, we argue that from its beginning the objective of the project to abolish border controls was to foster a supranational political identity of Union citizens by transforming citizens’ spatial experience. Union citizenship in the current EU Treaty framework constitutes the legal expression of that historical connection between the abolition of border controls and free movement. Emphasizing the citizenship dimension of an area without internal frontiers provides a different perspective on current controls at the Schengen internal borders.


A. Introduction
Controls at the internal borders between EU Member States have been formally abolished since the entry into force of the Convention Implementing the Schengen Agreement on March 26, 1995. Although border controls within the Schengen area "are meant to be a thing of the past," 1 "temporary" border controls have become quasi-permanent in five EU Member States since the "refugee crisis" of 2015. 2 The number of controls at internal borders increased in March 2020 when the first COVID-19 infections were detected in Europe and most Member States reinstated controls at their internal borders to prevent the spread of the virus.
Data on the reinstatement of checks at the internal borders illustrate the increase of border controls as an instrument to respond to perceived security threats in the Schengen area. In the nine years preceding September 2015, Member States reintroduced border controls a total of 40 times, while in the following five years -September 2015 -October 2020-this number rose to 237. 3 The continuous prolongation of border controls goes against the letter and spirit of the Schengen Borders Code, the principal legislative instrument that governs border management in the EU, and which permits only a temporary reinstatement of controls at internal borders. The result is a partial, de facto, suspension of Schengen. Although it is not uncommon for Member States to act in breach of their obligations under EU law, in those cases, the Commission normally avails itself of its enforcement powers, especially when an infringement of EU law extends over a significant period of time in a core area of European integration. Yet, at the time of writing -July 2021-the Commission has neither taken any formal steps to enforce the rules of the Schengen Borders Code, nor has it issued any political statement opposing the reinstatement of internal borders. 4 How did we arrive at this point?
The two principal theories of European integration -intergovernmentalism and neofunctionalism-consider the abolition of border controls in the Schengen area as a key area of integration. Yet, neither intergovernmentalism nor neofunctionalism adequately explains the current state of the Schengen area. While neofunctionalism is able to explain that the current Schengen system suffers from dysfunctionalities that follow after an external shock -prolonged reintroduction of border controls as response to the "refugee crisis"-5 it cannot explain why, despite the significant economic costs of maintaining border controls, 6 supranational actors, especially the Commission, have done so little to end the reintroduction of border controls. Intergovernmental approaches aptly show that Member States ultimately want to maintain their power to control immigration of third-country nationals, and are therefore reluctant to relinquish power over their borders, 7 which is often seen as one of the "'crown jewels' of national sovereignty." 8 As Thym and Bornemann observe, "Member States treat border controls as their quasisovereign domain." 9 Moreover, and especially so in times of crisis, Member States rely on the symbolic function of border controls to "convey a message of political power." 10 While we agree with this assessment, it does not explain why border controls effectively function as a symbol of Member State power. After all, the concrete function of a symbol is contingent on the structure of a discourse. Within legal discourse, border controls could represent an arbitrary exercise of state powers over Union citizens, 11 as much as a legitimate instrument to protect national security against external threats.
In our view, the current state of the Schengen area must also be considered as the result of a one-sided focus on the economic dimension of free movement, at the expense of Union citizens' rights; a focus which is reflected in much of the legal literature that sees the abolition of internal borders as primarily functional for the establishment of the internal market and the unimpeded free movement across borders for economic purposes. 12 This Article has a twofold objective. The first is to show that from the very beginning, the abolition of controls at the Member States' internal borders was connected to fostering a supranational political identity of Union citizens. More specifically, the project to abolish border controls had the objective to transform the way in which citizens experience space and ultimately the Union. Both the internal market project and the Schengen agreements share a common normative rationale and were the fruit of a shared political objective that went well beyond economic considerations. The second objective is to demonstrate that Union citizenship forms the legal expression of that historical connection between the abolition of border controls and free movement within the EU's current Treaty framework. This link between Union citizenship and the absence of border controls thus adds a political rationale to the more familiar economic foundations for the absence of border controls. Economic rationales have only weak legitimizing power and in times of crisis easily give way to a security rationale, namely a Member State's duty to protect its own citizens. By emphasizing the political dimension of free movement, we thus recalibrate the perspective on the current controls at the Schengen internal borders.
By looking at the political rationale behind Schengen, our Article links to recent literature on European integration which enquires into how the integration of core state powers-for instance in fiscal policy, migration control, or criminal justice-constitutes a driver for the creation of collective identities. 13 Recent scholarship shows that highly mobile Union citizens feel more European than less mobile Union citizens, which highlights the important function of free movement in the Union as a vehicle for identity formation. 14 The abolition of border controls shows how the transformation and creation of a common space -the abolition of physical border checks in an area of freedom, security and justice-serves a similar purpose.
The Article is structured as follows. Part B sets the background for this contribution and lays out the legal framework for the reintroduction of border controls and relates it to the practice of Member States and the Commission from September 2015 to May 2021. Part C shows that the abolition of controls of persons at internal borders was not merely based on an economic rationale of establishing the internal market, but also entailed an important political rationale of transforming citizens' spatial registers and thereby the way they would see the Union and themselves as Union citizens. In part D, the Article argues that this link between citizens and the abolition of border controls was, starting with the Amsterdam Treaty, gradually incorporated into the EU Treaty framework. This eventually resulted in a right of Union citizens to cross internal borders without being subject to border controls in the Lisbon Treaty. 15 The last partpart E-draws the consequences from the preceding analysis. At a meta-level, the partial suspension of Schengen negatively affects the way in which citizens relate to the Union and see themselves as Union citizens. At the level of positive law, the link between the abolition of border controls and Union citizenship in the Treaty framework calls for an interpretation of the exceptions in the Schengen Borders Code on reintroducing border controls in line with the exceptions to the free movement of EU citizens.

I. The Rules on the Reintroduction of Border Controls in the Schengen Borders Code
The core principle of the Schengen Border Code is that no controls on persons shall be conducted at the internal borders. The Schengen Borders Code includes two different grounds of exception from this core principle. The first derogation can be labelled the "ordinary" public policy or internal security exception. Article 25(1) Schengen Borders Code, which sets out the general framework for the reintroduction of border controls, provides that a Member State may exceptionally reintroduce controls at its internal borders where "there is a serious threat to public policy or internal security in a Member State." The Schengen Borders Code unambiguously states that reintroduction of controls can only be a means of last resort and the scope and duration thereof shall not exceed what is strictly necessary. The Schengen Borders Code distinguishes between foreseen threats in Article 25, such as major sporting events or political gatherings, and unforeseen circumstances in Article 28, such as terrorist attacks. The distinction is relevant for the maximum duration of controls and the notification procedure. In case of foreseen threats, the initial period of reintroducing controls is a maximum of 30 days and can be prolonged to a maximum of six months if the threat persists. In situations that require immediate action the initial period is a maximum of 10 days, which can be extended up to a maximum of two months. 16 Under the procedure of Article 25 of Schengen Borders Code, Member States only need to notify the Commission and the Council either in advance -foreseen circumstances-or as soon as possible -unforeseen circumstances-17 of their intention to reintroduce controls. 18 However, Member States must provide concrete reasons for the reintroduction of border controls, including details on the events that constitute a serious threat to public policy or internal security, 19 and assess the proportionality of the reintroduction of controls on the free movement of persons. 20 The second derogation can be labelled as a "specific" public policy and internal security ground -Article 29 Schengen Borders Code-, which was inserted in response to a political standoff in 2011 between France and Italy. France had closed its borders in response to Italy issuing temporary residence permits to large numbers of Tunisian migrants. 21 Whereas the ordinary exception ground refers to a threat to public policy or internal security in a Member State, Article 29 requires that there is "a serious ground to public policy or internal security to the overall functioning of the Schengen area," and that this risk is caused by "persistent deficiencies in the management of the external borders." Where this is the case, the Council may issue a recommendation that one or more Member States reintroduce controls at their internal borders, for renewable periods of up to six months, up to three times and with a maximum of two years. 22 Compared to the procedure under Article 25, the powers of the Member States are more narrowly circumscribed. It is only on the basis of a Council Recommendation that they are allowed to reinstate border controls for a prolonged period of time. 23 Moreover, the prolonged reintroduction is limited to narrowly defined exceptional circumstances subject to strict substantive and procedural requirements. 24 17 Id. arts. 25(1), (3). 18 Id. art. 28. 19 Id. art. 27(1). 20 Id. art. 26. 21 Sergio Carrera, Elspeth Guild, Massimo Merlino & Joanna Parkin, A Race Against Solidarity: The Schengen Regime and the Franco-Italian Affair, CENTER FOR EUROPEAN POLICY STUDIES (Apr. 29, 2011), https://www.ceps.eu/ceps-publications/ race-against-solidarity-schengen-regime-and-franco-italian-affair/. 22 Schengen Borders Code art. 29(1). Schengen Borders Code art. 25(4) provides that the maximum period for the reintroduction of controls shall not exceed two years, which raises the question of whether the maximum periods in arts. 25, 28 and 29 Schengen Borders Code are cumulative. Although the Commission suggested in the past that these grounds indeed are, the legal service of the Commission has argued that Schengen Borders Code art. 25(4) limits the period for the reintroduction of border controls to two years. Proposal for a Regulation amending Regulation (EU) 2016/399 as regards the rules applicable to the temporary reintroduction of border control at internal borders, COM (2017)  Art. 29(2) Schengen Borders Code provides that the "Council may, as a last resort and as a measure to protect the common interests within the area without internal border control . . . recommend that one or more Member States decide to reintroduce border control." The wording of this provision seems to suggest that a Council recommendation is not a necessary precondition for the reintroduction of border controls. Yet, the legislative history of the provisions suggests otherwise. When Art. 29 was inserted into the Schengen Borders Code by Regulation (EU) No 1051/2013 (2013 O.J. (L 295) 1), the extension of the maximum period for reintroducing border controls to two years was tied to common and more robust procedures and supervisory mechanisms. Then Commissioner for Home Affairs, Cecilia Malmström, commented that "we should not leave it only up to the member states at our external borders to deal with extraordinary migratory situations" and that such situations had to be resolved by a joint decision taken at European level by the Member States. Quoted in, Ruben Zaiotti, The Italo-French Row over Schengen, Critical Junctures, and the Future of Europe's Border Regime 28 J. BORDERL. STUD. 337, 341 (2013). Recital 9 of Regulation (EU) 1051/2013 stated that "implementing powers to adopt recommendations under that specific Union-level procedure should be conferred on the Council, acting on a proposal from the Commission." Accordingly, Regulation (EU) 1051/2013 provided that border controls "shall only occur on the basis of a recommendation of the Council." The Council recommendation should be based on a prior proposal of the Commission and an evaluation on the existence of serious deficiencies at the external borders. See also, STEVE PEERS, EU JUSTICE AND HOME AFFAIRS LAW 113 (2016), (arguing that "it appears that [the Member States] cannot exercise this power without a prior recommendation from the Council, in light of the 'exceptional' nature of the reintroduction of internal border controls"). 24 These exceptional circumstances relate to the inaction of Member States over findings of deficiencies in their management of their part of the external borders under the so-called Schengen Evaluation Mechanism or the Vulnerability Assessment Mechanism carried out by Frontex: Art. 29(1) Schengen Borders Code.

II. The practice of reintroduction of border controls and the failure of supervisory mechanisms
Despite the substantive and procedural requirements governing the use of the derogations in the Schengen Borders Code, when put to the test, these norms have turned out to be "fair weather rules." 25 Since 2015, border controls have been reinstated by five Member States on a quasipermanent basis: First, in response to the 2015 "refugee crisis" and the 2016 terrorist attacks in France, and since 2020 to counter the spread of COVID-19.
Although several European leaders have questioned the tenability of the Schengen rules or have openly called for their overhaul, 26 Member States generally notified the Commission and the Council and sought to justify the reinstatement of controls under the existing derogation grounds. In their notifications, Member States' invoke related but slightly different public policy and internal security concerns and thereby alternate between different exception grounds. In addition, Member States maintain that the reintroduction of border controls cannot be limited to the temporal limitations of the Schengen Borders Code in case of prolonged threats. This approach was accepted by the French Conseil d'État in two cases in which several non-governmental organizations requested annulment of the decision of the French government to prolong border controls for exceeding the time limits stated in the Schengen Borders Code. In both decisions, the Conseil d'État argued that in case of new ("nouvelle") or renewed ("renouvellés") threats, nothing stands in the way of restarting the clock and to prolong border controls beyond the time limits of the Schengen Borders Code. 27 In neither case did the Conseil d'État elaborate on what would constitute a new or renewed threat, nor did it decide to refer questions to the Court of Justice of the European Union (CJEU). In contrast, the Austrian Administrative Court of Styria which, in two cases pending before the CJEU at the time of writing, questioned the compatibility of the prolonged reinstatement of border checks by Austria. 28 Also, the Commission has been extremely reluctant in using its supervisory powers to protect borderless travel in Europe. The Schengen Border Code itself states that if the Commission has doubts on the necessity or the proportionality of a reintroduction of border controls, it "shall issue an opinion to that effect." 29 In its Proposal for a New Pact on Migration and Asylum of September 2020, the Commission stated that "[c]oncerns about existing shortcomings have contributed to the triggering of temporary internal border controls. The longer these controls continue, the more questions are raised about their temporary nature, and their proportionality." 30 However, with the exception of a single evaluation of the proportionality of the reintroduction of border controls in October 2015 by Austria and Germany, the Commission has never systematically evaluated these reinstatements, openly questioned their legality, or initiated infringement proceedings against Member States. In its opinion of October 2015, the Commission characterized Germany's reinstatement of border controls as adequate to counter the "identified threat to the internal security and public policy consisting of the uncontrolled influx of exceptionally large numbers of undocumented/improperly documented persons and the risk related to organized crime and terrorist threats," 31  third-country nationals should not per se be considered a threat to public policy or security. 32 Moreover, the Commission noted that the reintroduction had not prejudiced the rights of refugees to request asylum or the free movement of EU citizens. 33 In its communication on "preserving and strengthening Schengen" of 27 September 2017, the Commission noted that irregular entries into the EU and secondary movement have decreased significantly, 34 yet stopped short of criticizing the maintenance of border controls or to issue an opinion on their proportionality. The Commission merely recommended Member States to assess the proportionality of border controls and "encouraged" them to consider using police checks within the territory instead. 35 On the same day, the Commission published a proposal that sought to accommodate the security concerns of Member States, in what can be seen as an attempt to codify existing practice. This proposal would increase the maximum period under Article 25 Schengen Borders Code from six months to a year and allow for an extension to two years for situations in which serious threats to public order or internal security persist after that year. 36 Although the Council considered after 9/11 that temporary border controls are not an adequate response to the long-term threat of terrorism, 37 the Commission argued that "persistent serious threats to public policy or internal security [terrorism and secondary movements] . . . may require more time to deal with." 38 However, the proposal was never adopted and the Commission announced it will put forward a new proposal, which will also address exceptions based on public health, thus reaffirming that Member States retain the power to reintroduce border controls as a means of last resort. 39 The different reactions of the Commission towards the reintroduction of border controls related to irregular secondary movements in the Schengen area and terrorist threats, on the one hand, and border controls related to health reasons, on the other, show that the Commission has adopted a bifurcated approach towards public policy and internal security, depending on the concrete reasons for the reintroduction of border controls. When Member States reintroduced border controls in March 2020 to stop the spread of COVID-19, the Commission was willing to subsume the threat under the exceptions of public order and internal security, despite the absence of any specific reference to public health in the Schengen Borders Code. But the Commission also quickly established coordination procedures and announced that it would regularly assess the proportionality of border controls and request their lifting if they were found to be disproportionate. 40 On May 15, 2020, the Commission issued a communication in which it argued for "a return to unrestricted free movement of persons." 41 By contrast, with the exception of its opinion of October 2015 in which it held that the border controls by Austria and Germany were in compliance with the Schengen Borders Code, the Commission refrained from any evaluation of border controls that Member States prolong for almost six years for reasons of secondary movement of refugees or terrorist threats. 32 Pursuant to Recital 26 of the Schengen Borders Code: "Migration and the crossing of external borders by a large number of third-country nationals should not, per se, be considered to be a threat to public policy or internal security." 33 European Commission, supra note 31, at 7-8. The reason for the bifurcated approach of the Commission may, at least in part, be explained by the scale and economic influence of the border controls that were introduced in response to COVID-19. Yet, it may also be explained by the fact that the controls that aimed to control the movement of terrorists or irregular migrants were framed as measures countering external threats, whereas controls to stop the spread of COVID-19 by their nature aimed to control the movement of EU citizens. This, however, obscures the fact that the reinstatement of border controls primarily affects the rights of Union citizens, irrespective of the underlying rationale. 42 The Commission's initial emphasis was clearly on the economic dimension of free movement in the internal market: goods, services, and essential workers. Although the social dimension of restrictions on the free movement of EU citizens was given more attention at the later stages of the pandemic, border controls were only considered problematic to the extent that they interfered with the exercise of free movement rights and not as such. The Commission's focus on the economic dimension of free movement, is also reflected in legal literature on Schengen. This focus on the economic dimension of the abolition of internal border controls, as a corollary of the internal market project, often obscures the citizenship dimension of Schengen, which we turn to in the following part. The project of establishing an area without internal borders has been at the core of European integration since the Treaty of Rome. 44 The principal reasons for abolishing border controls between Member States were economic considerations; the free movement of goods, reduction of indirect costs, and an increase in competitiveness were considered necessary measures towards the establishment of a common market. However, already in the 1960s and the 1970s the abolition of border controls between Member States went beyond the economic sphere and was explicitly linked to political integration. By doing away with border controls between Member States, the Community ought to be made visible to the "man in the street," the ordinary citizen of the Community. 45 Although the Commission drafted several proposals that envisaged reducing formalities at internal borders in the 1970s, Member States considered these proposals as going too far and systematic checks at borders between Member States remained in place. 46  In its Communication of 1962, the Commission already argued that physical checks at the borders between Member States not only "prevent the establishment of a true common market, but also tend to obscure from the citizens of Europe the political significance of the undertaking embarked on by the six member states." European Commission, COM (62) 300 final. In another Communication to the Member States, the Commission argued that as long as Member States would continue to carry out physical checks at their internal borders "the citizens of the Community [would] continue to feel that there has been no decisive change." European Commission, Communication to the Council of Ministers of the EEC and to Member States Governments, at 3 (Oct. 2, 1962), http://aei.pitt.edu/53872/1/ECIS_10.2.62.pdf. 46 In 1975, the Commission suggested the creation of a common passport for the nationals of the Member States with the objective to represent the Community as a uniform entity vis-à-vis third countries and to ease border controls between Member States and transfer systematic controls to the external borders. European Commission, A Passport Union, COM secondary legislation, adopted to give effect to the provisions on the free movement of the nationals of the Member States, did limit the extent of such checks. In Pieck, the CJEU ruled that "any formality for the purpose of granting leave to enter the territory of a Member State which is coupled with a passport or identity check at the border, at whatever place or time and in whatever form" would amount to an "entry visa or equivalent requirement" and would thus be prohibited. 47 Border guards may not inquire about the purpose and duration of stay or the financial means of the EU citizen before permitting entry. 48 And although Member States were still permitted to carry out identity controls, the Court limited these controls: When identity controls take place at the time of entry into a Member State's territory, they constitute a barrier to free movement when carried out in a systematic, arbitrary or unnecessarily restrictive manner. 49 The key documents on abolishing border controls in the 1980s were the Commission's 1985 White Paper on the Creation of the Single Market and the Single European Act. Although the White Paper did not offer significantly more than what the Treaties and the case law of the Court of Justice had already provided for, 50 it introduced a subtle but remarkable change of rhetoric. Whereas previous policy documents sought to change the mode of border controls, the White Paper questioned the very existence of border controls. The Commission made clear that the objective of the White Paper was not merely to ease existing border procedures "but to do away with internal frontier controls in their entirety." 51 For this, the Commission advanced two sets of arguments: The first based on a market rationale, the second on a political rationale. Both rationales entailed specific arguments and assumptions about the market, competition, and modes of integration, as well as distinct conceptions of space.
Under the market rationale, the Commission advanced economic arguments, stating that "[t]he reason for getting rid entirely of physical and other controls between Member States is not one of theology or appearance, but the hard practical fact that the maintenance of any internal frontier controls will perpetuate the costs and disadvantages of a divided market." 52 Border controls were conceived as inefficient means of controlling substantive policy domains, such as public health, veterinary inspections, VAT collection, and transport safety, which could be more efficiently governed through harmonization, administrative cooperation, and, if necessary, spot checks. 53 The reasoning behind this rationale was formal, technical, and bore an aura of necessity. It translated physical border controls into economic figures and calculated their direct and indirect costs. 54 It argued that the abolition of controls was to take place through harmonization and the use of technical bodies, such as the European Standardization Organizations. 55 See Cornellise, supra note 7. 53 Id. See also European Commission, Abolition of Controls of Persons at Intra-Community Borders, COM (88) 640 final (Dec 7, 1988), in particular para. 7. 54 In this formal jargon, the free movement of students and researchers is conceived of as "making better use of human resources, in particular by means of increased mobility," as the European Council put it at its meeting preceding the White Paper. See European Council, March 29-30, 1985, SN 1381/2/85, 5, https://www.consilium.europa.eu/media/20653/ 1985_march_-_brussels__eng_.pdf. 55 On the technical rationale of the White Paper, see the contributions in 25 J. COMMON MARK. STUD (1987).
And it presented the need to do away with border controls as the inevitable result of structural changes in the global economy, necessary to maintain economic competitiveness on a global scale. The specific conception of space is that of a market, a synthetic formal space that is governed by technocrats and rationally ordered to achieve specific objectives -such as, higher competitiveness, efficiency, and reduced costs. 56 In this market space, the rationale for abolishing border controls is functional: It is a means to realize the internal marketand not an end in itself.
Yet, the drafters of the White Paper were aware of the weak legitimacy of the market rationale and the need for a broader political narrative. 57 Thus, the White Paper linked the abolition of border controls to the discourse of constructing European citizenship. The crucial difference between the market rationale and the political rationale is that while behind the market rationale the abolition of border controls is a means to establish the internal market, the abolition of border controls in the political rationale is an end in itself. Borders are constitutive of political communities and, more precisely, of liberal conceptions of citizenship. 58 The European Council meeting at Fontainebleau in June 1984 had already considered it essential to "respond to the expectations of the people of Europe by adopting measures to strengthen and promote its identity and its image both for its citizens and for the rest of the world." 59 The Council established an Ad Hoc Committee on a People's Europe, which recommended the implementation of measures that facilitate the freedom of movement of Community citizens across intra-Community land borders as the easiest way to provide the citizens of the Member States with "tangible benefits in their everyday lives." 60 Only three months afterwards, the Commission in its White Paper adopted a similar line of reasoning, when suggesting the full abolition of intra-Community borders: It is the physical barriers ( : : : ) which to the ordinary citizen are the obvious manifestation of the continued division of the Communitynot the 'broader and deeper Community' envisaged by the original Treaties but a Community still divided. And it continued: Even though these controls are often no more than spot checks, they are seen as the outward sign of an arbitrary administrative power over individuals and as an affront to the principle of freedom of movement within a single community. 62 There are two aspects to the White Paper's terminology. First, although no Community legislation existed which requires the abolition of controls at intra-Community borders, the White Paper nevertheless states that the principle of free movement mandates the abolition of border controls. This is essentially a legal argument. However, the White Paper does not explain the legal reasoning that mandates the abolition of border controls, but rather employs legal terminology to advance an argument about European integration. This is linked to the second aspect. Free movement is couched in a narrative that construes border controls as material obstacles that prevent citizens from seeing the progress of European integration. If border controls, as physical outward signs that divide different Member States, were removed, citizens would be able to see a single Community instead of different national jurisdictions. The objective of abolishing border controls in the White Paper aimed at transforming the way citizens would see the Community. 63 Like a state, the Community requires a material manifestation to become real in the political imagination of citizens. 64 Interestingly enough, the terminology of the White Paper was not merely a bold pitch of Brussels-based elites, but reflected and dwelled on prior historical events; in particular, as we argue below, on the protests of truck drivers against border controls in several Member States that occurred one year before the publication of the White Paper. 65

II. Schengen as 'Test' Laboratory for the Internal Area Without Borders
The Single European Act was adopted to enable the completion of the internal market as envisaged by the White Paper. It inserted Article 8a into the European Economic Community (EEC Treaty) 66 , which defined the internal market as "an area without internal frontiers in which the free movement of goods, persons, services and capital is ensured in accordance with the provisions of this Treaty." 67 However, disagreement arose as to the definition of the internal market as an area without internal frontiers. This is best illustrated by Margaret Thatcher's speech at the College of Europe in 1988. While the UK government supported the neo-liberal idea of borderless trade, Thatcher made clear that she regarded it "a matter of plain common sense that we cannot abolish frontier controls if we are also to protect our citizens from crime and stop the movement of . The frequent references to the importance of the psychological aspect of the visibility of border controls, both in the White Paper and in the preceding policy documents concerned with abolishing controls, suggest that the drafters of the White Paper were, at least, aware of the importance of modifying material space for political consciousness. Lord Cockfield, the architect of the White Paper, argued that "one can see a lorry carrying goods stopped at the frontier: but you cannot see a banking service or insurance stopped at the frontier." LORD COCKFIELD, supra note 57, at 24. 64 Ethnographic scholarship emphasizes how both concrete institutions and languages, or ideas, of government and authority constitute the modern State. drugs, of terrorists and of illegal immigrants." 68 The idea that the lifting of internal borders triggered a security question, was not exclusive to the UK. The White Paper itself recognized a need for "alternative means of protection for controls at the internal borders and to strengthen those already existing." 69 However, where the UK and other Member States differed was where and by whom this security concern was to be addressed. 70 In June 1989, the Madrid European Council approved a work program for the establishment of an area without internal frontiers, the so-called Palma Document, but noted the political divergences "on the interpretation and scope of the relevant Treaty provisions inter alia 8A EC and the obligation flowing therefrom . . . and where the competence for taking decisions and action lay [to adopt the measures deemed necessary to allow for the abolition of internal borders]." 71 The way forward was intergovernmental. Under the responsibility of the immigration ministers, work started on a Convention on crossings at the external frontiers of the Member States. 72 This resulted in the Member States reaching agreement in June 1991. Although a Declaration attached to the Convention stated that it was signed "with a view to achieving the objectives of Article 8a [EEC]," that same Declaration made clear that it did not "contain any express or implicit obligation upon Member States concerning controls at intra-Community frontiers." 73 Ultimately, disagreement between the UK and Spain over the status of Gibraltar prevented the Convention's signature. 74 It was the lack of progress within the Community framework that allowed Schengen, as a parallel initiative to abolish border controls between continental Member States, to gain practical and legal significance. With the signature of the Schengen Agreement in June 1985, Germany, France, and the Benelux countries took the principled decision to abolish border controls between their territories. Subsequent accession agreements were signed with other EU Member States, except the UK and Ireland. The Schengen Agreement set out some immediate measures; for instance, the easing of formalities at border controls, 75 reinforcement of cooperation of police authorities, and approximation of rules. 76 The actual lifting of controls at internal borders, however, was made dependent on the adoption of a set of common rules in the field of external borders, migration, asylum, and police cooperation. The adoption of these common rules aimed to offset the alleged  security deficit that would result from the abolition of internal borders and was foreseen by January 1, 1990. 77 It took five years to adopt these so-called "flanking measures" in the Schengen Implementing Convention (CISA). Unlike the Schengen Agreement, the CISA included the abolition of border controls as a legal obligation and not merely as an objective to be realized in the future. In March 1995, all Schengen participating states, with the exception of France, had abolished controls at their internal borders. 78 Two years later, the Member States, in the Treaty of Amsterdam, decided to incorporate the Schengen acquis in the EU legal order.
Although the development of Schengen under international law can be formally regarded as separate from the internal market project and thus EU law, the two cannot be regarded in isolation. 79 They took place at the same time, involving the majority of Member States and, most importantly, shared an underlying rationale that transcended considerations of an economic nature. Three examples illustrate this: The events that eventually resulted in the adoption of the Schengen Agreement in 1985, the scope of the CISA, and the measures adopted to implement the CISA.
First, the origins of the Schengen Agreement lay in a "symbolic initiative" 80 taken by Germany and France to relax checks for car drivers, which led to protests by French, German, and Austrian lorry drivers, who continued to be stopped at internal borders. Although economically motivated, these protests cannot be reduced entirely to a market rationale: The protests were widely regarded as targeting controls that "should have ceased to exist." 81 These protests eventually resulted in the conclusion of the Saarbrücken Agreement, which formed the blueprint for the conclusion of the Schengen Agreement one year later. 82 Second, the preambles of both the Schengen Agreement and the CISA explicitly refer to the objectives of the European Community. The Schengen Agreement stated that "the ever closer union of the peoples of the Member States of the European Communities should find its expression in the freedom to cross internal borders for all nationals" and that the removal of obstacles to free movement would "strengthen solidarity between them." 83 The CISA added a specific reference to the Single European Act and the internal market as an area without internal frontiers. It also affirmed that it would not prejudice the objectives of the European Community. The Schengen process soon came to be regarded as a "laboratory" for a common European space without borders, 84 a form of enhanced cooperation avant la lettre, and was broadly understood as part and parcel to the construction of an area without internal borders. 85 Commission officials and 77 Didier Bigo has pointed out the "mythical" nature of the security deficit that would result from the abolition of border controls between Member States. The "need" for compensatory measures and the alleged security deficit were discursively constructed in an institutional environment that was heavily dominated by officials of national ministries of interior. See, Didier Bigo, Border Regimes, Police Cooperation and Security in an Enlarged Europe, in EUROPE UNBOUND: ENLARGING AND RESHAPING THE BOUNDARIES OF EUROPE 214 (Jan Zielonka ed., 2003). 78 France maintained controls at its internal borders, essentially due to the Netherland's liberal drugs policy. The other Schengen states, in particular Germany and Netherlands, insisted that the maintenance of controls by France was contrary to CISA art. 2(2). See Kees Groenendijk, supra note 37, 156-58. representatives of Member States endorsed the view that the Schengen cooperation concerned Community boundaries, which is also confirmed by the definition of alien under the CISA as anyone not holding the nationality of a Member State.
Third, the explicit links to the European project already show that the Schengen acquis sought to create more than just an internal market. This is particularly obvious from one of the key decisions adopted by the Schengen Executive Committee in April 1994 for the implementation of the CISA, concerning the reduction of obstacles to traffic flows. The brief and single operative paragraph of the decision simply states that material structures at border crossing points must be removed, as they constitute obstacles that hinder free movement and traffic across internal borders. 86 However, the Annex to the Decision goes much further than merely ensuring unhindered crossing of the border and suggests to either dismantle entire border structures and facilities or putting them to another use. This can only be understood when seen in the light of the objective to transform the sensory perceptions of citizens of the Union as a single spatial entity.

III. Meeting Mr Wijsenbeek
The Maastricht Treaty repeated the objective of establishing an internal market as an area of free movement without internal frontiers. 87 Yet, despite this unambiguous wording and the objective to complete the internal market by December 31, 1992, the failure to adopt the External Frontiers Convention meant that internal border controls were not lifted by this date. 88 Frustrated by the lack of progress, a group of integration-minded Members of the European Parliament (MEPs) tried to force a judicial breakthrough by seizing the CJEU of the matter. In previous situations of political deadlock, the CJEU had proven instrumental in giving full effect to the provisions of the Treaties and strategic litigation has been at the basis of some of the classic cases of EU law. 89 The case that eventually reached the CJEU, by way of preliminary reference, was that of Dutch MEP Floris Wijsenbeek. Upon arriving from Strasbourg at Rotterdam airport, which only operated intra-Community flights, Mr. Wijsenbeek refused to show his passport. He was fined for violating Dutch immigration law and the Dutch Court of Appeal eventually referred a straightforward set of questions to Luxemburg: Do Articles 7a, -now Article 26 TFEUand 8a -now Article 21 TFEU-of the Treaty establishing the European Community (EC Treaty) preclude Member States from imposing an obligation to present a passport at intra-Community borders? 90 The standard account of the Wijsenbeek decision is that the Court held that neither Article 7a nor Article 8a of the EC Treaty had direct effect, since both Treaty provisions required the adoption of implementing legislation. The CJEU therefore concluded that, absent any harmonized rules on the controls of external borders, visa, and asylum, Member States retain the right to carry out border controls. 91 This account, however, overlooks the legal nuances of the decision.
There is an important part of the judgment that focusses on the role of Union citizenship. Both the Commission and Advocate General Cosmas made a clear distinction between free movement rights in the market sphere -Article 7a EC Treaty-and citizenship -Article 8a EEC Treaty. The Commission argued that while free movement in the market sphere requires the adoption of harmonization measures on external borders, the right of citizens to move freely across borders is "recognised directly in that provision, without any reservation and without the slightest scope for the exercise of discretion." 92 Although the Commission argued that the right of citizens has "incontestabl[y]" direct effect, the Commission considered that it may be subject to limitations foreseen in the Treaty; as long as no harmonized rules on external borders were adopted and put in place, the Commission argued, Member States could require Union citizens to show valid travel documents at the internal borders. 93 This distinction between free movement rights that pertained to the market sphere and free movement rights that pertained to the political sphere, in the context of border controls, is even more pronounced in the Opinion of the Advocate General. Advocate General Cosmas argued that the former "have established a functional possibility for nationals of the Member States . . . with a view to the creation of a common market, the objective of which can only be to permit persons to pursue their economic activities in optimum conditions." 94 In other words, the abolition of border controls -and the rights linked to it-in the market sphere are functional to creating the internal market. By contrast, citizens' rights to free movement differ categorically from the rights in the market sphere; they constitute, as Advocate General Cosmas argued, "a right of a different kind, a true right of movement, stemming from the status as a citizen of the Union." 95 He continued: Hence, as freedom of movement constitutes a goal in itself and is inherent in the fact of being a citizen of the Union, and is not merely a parameter of the common market, it does not merely have a different regulatory scope: it also, and primarily, differs in terms of the nature of the rights it bestows on individuals and the breadth of the guarantee that Community and national principles must accord it. 96 Thus, the freedom of nationals of Member States to enhance their economic benefits would not be "seriously threatened" by the requirement to show a valid travel document at the border; by contrast, the freedom of Union citizens would be seriously infringed by the requirement to show a travel document at the border. 97 Why? Because the "freedom to cross borders is in itself an important constituent of the citizen's right to move freely, and not simply a means of achieving the common market. Moreover, recognition of the possibility of moving -in principle-unchecked within the geographic area corresponding to a legal order is inherent in the status of citizen covered by that legal order." 98 Similar to the Commission's legal opinion, Advocate General Cosmas concluded that the overriding public interest in the absence of harmonized rules on Wijsenbeek, Case 99 Against the background of the elaborate arguments of the Commission and the Advocate General, it is interesting to see what the CJEU did and did not say in its short reply to the questions put before it. It is interesting to note the difference between the Court's arguments on free movement in the market sphere and in the political sphere. As regards the market sphere, the Court followed the Commission and the Advocate General and unambiguously held that no automatic obligation arises from Article 7 EC Treaty to abolish border controls after December 31, 1992, because it presupposes harmonization of rules on external borders. 100 As clear as the Court's argument was in regard to the market sphere, as enigmatic was its ruling in relation to Union citizenship. The Court merely stated that as long as EU legislation on external borders was absent "the exercise of those rights presupposes that the person concerned is able to establish that he or she has the nationality of a Member State." 101 In the following paragraph the Court added that even if under Article 21 TFEU Union citizens were to "have an unconditional right to move freely within the territory of the Member States," which indeed it later held to be the case in Baumbast, 102 Member States retained the right to carry out identity checks at the internal frontiers of the Community. 103 The Court thus argued that Article 8a EC Treaty, as was submitted by the Commission, can be justifiably limited. While it referred to the declaration on Article 7a EC Treaty, that the date of December 31, 1992 does not create automatic legal effect, it did not refer to the same declaration on Article 8a EC Treaty 104 nor to the UK and Ireland's arguments that Article 8a EC Treaty does not have direct effect. As it did in earlier cases, 105 the Court made a distinction between the existence and the exercise of free movement rights of citizens. 106 It clearly stated that the exercise, and not the existence, of citizens free movement rights presupposes EU legislation on external borders. 107 The CJEU thus recognized, albeit implicitly and subject to the conditions of flanking measures, such a right to free movement based on the Treaty's provision on Union citizenship.
It is important to realize that the Court upheld the distinction between free movement rights in the market sphere and free movement rights in the political sphere. By connecting the latter to the abolition of border controls the Court created a link between Maastricht's -intergovernmentalthird pillar on justice and home affairs and its -supranational-Community pillar and confirmed the link between the abolition of border controls and Union citizenship. See Rijpma, supra note 72, at para. 38. 105 Case C-85/96, María Martínez Sala v. Freistaat Bayern, 1998 E.C.R. I-02691, paras. 61-64. The Court argued in Martinez Sala that "it is not necessary to examine whether the person concerned can rely on Article 8a of the Treaty in order to obtain recognition of a new right to reside in the territory of the Member State concerned, since it is common ground that she has already been authorised to reside there, although she has been refused issue of a residence permit." 106 On this argument see Helen Toner, Passport Controls at Borders Between Member States 25 EUR. LAW REV 415, 420 (2000). 107 Wijsenbeek, Case C-378/97 at para. 42. not to upset the comprise negotiated in the Amsterdam Intergovernmental Conference, which incorporated the Schengen acquis into the EU legal order at the cost of a variable geometry in this area.

D. The Absence of Border Controls as Fundamental Objective of EU Law
Still, the Court could have simply accorded direct effect to the absence of internal frontiers. In quite a few internal market cases the Court was not deterred by the absence of harmonizing measures. To the contrary, legislative inaction was often at the basis for according direct effect to provisions of primary law. 108 The argument that this would have resulted in a "regulatory gap" does not convince, because the third pillar did provide the Union with powers in this field, and alternatively such powers were implied in the legal basis provisions on the free movement of persons.
More importantly, the objective of the strategic litigation in Wijsenbeek-to abolish controls at internal borders-had already materialized when the Court of Justice delivered its decision in September 1999. The Treaty of Amsterdam had entered into force on May 1, 1999 and incorporated the abolition of border controls into the EU legal order. It did so in a twofold way.
First, the Treaty of Amsterdam incorporated the Schengen acquis into EU law through Protocol No. 2, 109 thus "bringing to life the decades-old vision of a Europe without internal border controls." 110 It obliged the Council to adopt common measures on asylum within five years, external borders and visa for third-country nationals that aimed at ensuring the free movement of persons. 111 Until that moment, however, the compensatory measures of the Schengen acquis were considered as acts of secondary legislation. 112 Second, the Treaty of Amsterdam established a link between citizens and the Schengen acquis by including the area of freedom, security and justice (AFSJ) as an objective of the Union into the Treaty framework. 113 The establishment of the AFSJ was based both on a market rationale and a political rationale. On the one hand, the measures on migration, asylum, visa and borders clearly stand in function of the economic dimension of the free movement of persons. 114  brought by the UK against the Council, the Court of Justice ruled that a Member State can only participate in a measure of the Schengen acquis, if it accepted the area of the Schengen acquis on which that measure builds. As the UK had not accepted the rules on abolishing internal border controls, it could be validly excluded from Frontex, the European Border and Coast Guard Agency, and the Regulation on security features in passports. 115 On the other hand, the establishment of an AFSJ clearly goes beyond the internal market rationale. The Turin European Council, which constituted the opening session of the Intergovernmental Conference, had identified the objective of bringing "the Union closer to its citizens" as one of the central themes for the Conference and had grouped the substantive policy fields of the AFSJ under this heading. 116 The Treaty of Amsterdam inserted the aim to develop the EU as an AFSJ in which the free movement of persons is guaranteed as a new Union objective in the Treaty framework, in addition to the internal market objective. 117 In line with this, the Tampere European Council Conclusions, the first five-year strategic plan for the development of the AFSJ, described the area as "a project" that "responds to the frequently expressed concerns of citizens", "has a direct bearing on their daily lives" and freedom as the "right to move freely throughout the Union." 118 The title of Tampere's successor program, the Stockholm Programme confirmed this political dimension, promising "an open and secure Europe serving and protecting the citizens." 119 A common critique of this political dimension is that security constitutes the overriding imperative, thus crowding out freedom and justice. It has been argued that the incorporation of the Schengen acquis into the EU legal order "Schengenized" the Union and codified the narrative that free movement internally can only be achieved by more restrictive compensatory measures. 120 While this is certainly true, we caution to consider the AFSJ only from a security perspective. By the Court's own logic in Wijsenbeek, what is required is simply a framework for the management of the external borders; it did not impose any additional conditions as to the substance or effectiveness of these rules. 121 Moreover, the lifting of internal border controls was deliberately premised on the idea of mutual recognition and limited harmonization, the so-called flanking measures. This logic remains present until today in the distinction between Schengen developing measures and other measures covered by Title V in the TFEU on the AFSJ. A lack of progress in AFSJ policy fields, such as the Common European Asylum System or criminal justice cooperation cannot be invoked to question the absence of border controls -although it might negatively affect Member States' views on a borderless Schengen.
Like earlier Commission and Council documents on the abolition of border controls, which were discussed in the preceding section, the notion of citizen refers to Union citizens in a political register-and not as a formal legal status. The Treaty of Amsterdam did not link the AFSJ to the formal legal status of Union citizenship, a link that was established only explicitly in the Lisbon Treaty, but the notion of citizen also went beyond holding the nationality of one of the Member States. After all, the objective of including the AFSJ into the Treaty of Amsterdam was not merely to abolish border controls but "to develop [the EU] more rapidly into an area of freedom, security and justice." 122 Thus, the inclusion of the AFSJ into the Treaty of Amsterdam sought not merely to construct a "new kind of policy whole," 123 but also to construct a common area. Had the Treaty drafters sought to establish merely different policy fields, they could have used freedom, security and justice tout court. However, they included the spatial notion of area and linked these three values to the area. By including the notion of area in the AFSJ, the Treaty drafters shifted the rhetoric of integration from a negative -absence of internal border controls-to a positive -construction of a common area-semantic.
The AFSJ as a common area of the Union entails two features. First, the AFSJ constitutes a geographic space where border controls are abolished and citizens can move freely without being subject to border controls. In order to establish and maintain this geographic space where internal border controls are abolished, the power of the EU institutions was enhanced: The Commission was given increased powers of initiative in all areas of the AFSJ, the Justice and Home Affairs Council preserved institutional unity across the different policy domains, and the European Council in Tampere in October 1999 set out concrete policy objectives to develop the AFSJ.
Second, the area as geographic space is normatively qualified by the values of freedom, security and justice. This dual dimension of the AFSJ-a concrete geographic space and a normative space -points to a deeper meaning of the notion of citizen in the political register: The relation between citizenship and space. For Hanna Arendt, the realization of freedom and equality-the hallmarks of modern citizenship-as a tangible concrete reality is the result of a decision taken by a political community to accord to its members equal rights: "We are not born equal; we become equal as members of a group on the strength of our decision to guarantee ourselves mutually equal rights." 124 As a community is necessarily located somewhere, the realization of freedom and equality requires spatial boundedness, which, as Arendt argued, was "especially clear for the greatest and most elementary of all negative liberties, the freedom of movement." 125 If Arendt's argument is transposed to the AFSJ: The abolition of internal border controls and the creation of a common external border established a territorially bounded place in which free movement is realized as a tangible reality. Hans Lindahl argues that "values are a constitutive feature of territoriality"; by deciding which values are legally relevant and which values are not, a community -in this case: the ensemble of Union citizens-relates to that space and creates its "own place." 126 To be clear, it is only in the abstract that the geographic and the normative features of the AFSJ as a legal place can be held apart. A legal place always involves territorial boundedness and at the same time a decision which values are legally relevant in that place. Therefore, how a community understands itself is constantly reinterpreted by how that community relates to itself, mediated by its "own" place. 127 It is in these registers of political theory that the Treaty of Amsterdam linked the AFSJ, as a bounded place where freedom is actualized as free movement of citizens, to Union citizens. It was only in the Lisbon Treaty, as we argue in the following section, that Union citizenship as a formal legal status was explicitly linked to the AFSJ.

II. The Lisbon Treaty: Linking AFSJ and Union Citizenship
In the Lisbon Treaty, 128 the political aspect of the AFSJ was given further prominence. Whilst the Treaty of Amsterdam had mentioned the internal market objective before the AFSJ, and the Draft Constitution placed the AFSJ and the internal market at the same level, Article 3(2) TEU positions the AFSJ above the internal market. Unlike in the Treaty of Amsterdam, the substantive provisions on the AFSJ in Title V of the TFEU lack a reference to free movement in the internal market. These are not merely semantic differences, but reflect both the increasing significance of the AFSJ in the constitutional framework of EU law and its gradual emancipation from the economic rationale of the internal market. 129 The Lisbon Treaty further elevates the political dimension of free movement in a twofold way: It proclaims that the AFSJ constitutes an area without internal frontiers 130 and explicitly links the area to Union citizenship. 131 Article 3(2) TEU states that the "Union shall offer its citizens an area of freedom, security and justice without internal frontiers, in which the free movement of persons is ensured." The claim that the AFSJ is an area without internal frontiers does not merely constitute a Treaty objective but is further developed in the Treaty title on the AFSJ. Article 67(1) TFEU first states that the "Union shall constitute an area of freedom, security and justice" and the subsequent paragraphs programmatically relate to these three values and attach concrete legal substance to them. Article 67(2) TFEU begins the enumeration with the notion of "freedom" and states that the Union "shall ensure the absence of controls at the internal borders for persons." In the terminology of political theory, Article 67(2) TFEU legally concretizes the abstract notion of freedom by making it a tangible reality to move within the Union unhindered by internal border controls. This is highlighted in the case law of the Court of Justice on Article 67(2) TFEU.
In Touring Tours, the Court held that Article 67(2) TFEU is not merely a programmatic provision, but also entails a primary law obligation that extends to Member States. This case concerned German legislation that imposed a general obligation on private transport companies to check the travel documents of passengers before they boarded a bus in intra-EU journeys and financial sanctions in case of non-compliance. Most of the legal reasoning in Touring Tours is concerned with the question whether the German legislation amounted to measures having the equivalent effect of border controls, prohibited by Article 23 of the Schengen Borders Code, which the Court ruled to be the case. 132 However, the Court did not stop there and held that Article 67(2) TFEU also "precludes such legislation." This finding was anything but obvious. The wording of Article 67 does not refer to the Member States, and the Court itself had decided in earlier cases that Article 67 is principally addressed to the Union. 133 The Court also did not need to refer to Article 67(2) TFEU to find that the German legislation violated EU law. In consequence, by anchoring an obligation on the side of the Member States -and not merely the Union-to ensure the absence of border controls directly in the substantive Treaty provisions on the AFSJ, the Court underscored the constitutional nature of the obligation to abolish border controls in the EU. 134 The Court's decision in Touring Tours illustrates a second aspect: The link between the abolition of border controls in the AFSJ and Union citizenship. Both the wording of Article 21 TFEU and Article 45 of the EU Charter of Fundamental Rights entail the right of Union citizens to "move and reside freely within the territory of Member States." In Wijsenbeek, the Court left the question of whether the citizenship provisions in the Treaty encompass a right not to be subject to border controls unanswered. In his Opinion in Touring Tours, Advocate General Yves Bot suggested that the right of free movement includes a right not to be subject to border controls: "For citizens of the European Union, the right to move freely and unhindered within the territory of the Member States constitutes a fundamental right in accordance with Article 3(2) TEU and Article 20(2) and Article 21 TFEU." 135 As the facts of the case concerned German legislation that was considered to have equivalent effects to border controls, the "right to move freely and unhindered" arguably entails a right to move across internal borders without being subject to border controls. Movement could barely be described as free and unhindered if it was subject to controls.
The Court in Touring Tours did not take up the Advocate General's argument that the citizenship provisions in the TFEU include a right not to be subject to controls at internal borders. Rather, the Court left it open whether such a right flows directly from the citizenship provisions in the Treaties -primary law-or merely from the Schengen Borders Code -secondary law-). However, the Court's silence on this issue should not be overstated. Already in earlier cases, the Court had stated that the right to "to enter the territory of another Member State and reside there for the purposes intended by the Treaty is a right conferred directly by the Treaty or, as the case may be, by the provisions adopted for its implementation [the Citizenship Directive]." 136 Thus, as the Court suggested, what the right to enter entails has to be considered in light of the provisions of the Citizenship Directive, which gives effect to the free movement rights in Articles 20 and 21 TFEU. Therefore, the right to enter another Member State in Article 5 Directive 2004/38 -Citizenship Rights Directive-is one particular aspect of the broader right of free movement in the Treaty provisions. In the past, the Court had held that Member States must not make the right of entry subject to any additional conditions that are not included in Union law. 137 As the abolition of border controls essentially aims to ensure the free movement of Union citizens, as we argue above, the provisions in the Treaty and the Citizenship Rights Directive on free movement of Union citizens must be read in connection with the Schengen acquis, in particular the provisions on the abolition of controls at the internal borders. 138 This, however, raises the question on the exact relation between the free movement rights of Union citizenship and the rules of the Schengen Borders Code. This relation includes two different aspects.
The first aspect is a negative relation between Union citizens free movement rights and the Schengen Borders Code: The application of the provisions in the Schengen Borders Code should not impede free movement rights of Union citizens and must be in accordance with the rights in the Citizenship Directive. 139  The Schengen Borders Code refers to the Citizenship Rights Directive, stating that the rules of the Schengen Borders Code shall not affect the free movement rights of Union citizens under recital (5) and Article 8(6) of the Schengen Borders Code. Likewise, the Citizenship Rights Directive states that the "formalities connected with the free movement of Union citizens within the territory of Member States should be clearly defined, without prejudice to the provisions applicable to national border controls." Recital (7), Directive 2004/38. not have the purpose "to restrict the freedom of movement of Union citizens as provided for by the FEU Treaty." 140 The second aspect is a positive relation in the sense that the rules of the Schengen Borders Code enable Union citizens to move freely in the Schengen area. As Elspeth Guild and others have argued, the provisions of the Schengen Borders Code are of "particular relevance to the practical exercise of the right of exit and entry provided for in Articles 4 and 5." 141 The historical development of the Schengen acquis, as we argue above, was based on a political rationale to enhance free movement of citizens. Thus, the positive relation between the Schengen acquis and free movement rights in the citizenship provisions means that Union citizens should, in principle, not be checked at all when crossing an internal border. Article 5 of the Citizenship Directive states that "[w]ithout prejudice to the provisions on travel documents applicable to national border controls, Member States shall grant Union citizens leave to enter their territory with a valid identity card or passport . . . ." According to Advocate General Szpunar, the fact that the current wording of this Article -"with"has replaced "on production of" in earlier legislation, reflects the lifting of checks at the internal borders. 142 As such, this Article could only be validly invoked by Member States to ask a Union citizen to show their travel documents if this Member State: (i) has obtained an opt-out from the Schengen cooperation; (ii) does not yet apply the Schengen acquis in full; or (iii) has temporarily reintroduced controls at their internal borders under the Schengen Borders Code.

III. Géometrie Variable of Citizenship Rights?
If the scope of the right to free movement in the citizenship provisions in the TFEU entails a right not to be subjected to controls at internal borders, how can this be squared with the fact that some Member States-Ireland, Croatia, Bulgaria, Romania-are not yet part of the Schengen area and still have controls at their internal borders to other Member States in place? Would this not result in a geographical fragmentation of citizenship rights? Union citizens could rely on the right not to be subjected to border controls in Germany, while they would not be able to do so in Ireland.
A géographie variable of citizenship rights is the consequence of political compromises that resulted in differentiated levels of integration. Two forms of differentiated integration can be distinguished in the Treaty framework. First, the special position of Ireland and Denmarkand formerly the UK-in the Schengen framework 143 constitutes a form of "constitutional differentiation." 144 Constitutional differentiation means that the particular legal position of these Member States is enshrined in the Treaty framework, is likely to be permanent and concerns the reluctance of these Member States to transfer critical core competences to the EU. Second, the special position of the "new" Member States -Bulgaria, Croatia, Romania, Cyprus-can be described as "instrumental differentiation." 145 Contrary to constitutional differentiation, instrumental differentiation is temporary and results from a perceived lack of factual harmonization. The Schengen Protocol clearly states that newly acceding Member States are under an obligation to participate in the Schengen rules. The upshot is that the refusal of the Council to fully apply the rules of the Schengen acquis, in particular the principle of the absence of controls at the internal See Cornelisse, supra note 7, at 752-53. 145 Id.
borders, should continue only for as long as these Member States are considered not being able to adequately control their external borders. However, the fact that these countries have been effectively kept in Schengen purgatory based on political concerns unrelated to the management of the external border, 146 does raise important concerns in relation to the citizenship rights of the nationals of these countries.
Both constitutional and instrumental differentiation, however, are exceptions to the general rule of the abolition of controls at the internal borders-and therefore to the right of citizens to move freely across an internal border without being stopped and having one's travel documents checked.

E. The Reintroduction of Border Controls From a Union Citizenship Perspective
So far, we have submitted that Member States maintain controls at their internal borders against the letter and the spirit of the Schengen Borders Code and they do so largely unchecked. The failure of the Commission to enforce EU law rules on the absence of border controls and the lack of assessing the effects of citizenship rights by Member States derives in part from the focus on the economic dimension of free movement. Indeed, both the European Parliament and the Commission have documented the economic costs of the de facto partial suspension of Schengen. 147 Unlike the economic costs of non-Schengen, the effects of the long-term reintroduction of border controls on citizenship cannot be easily quantified and are less obvious. Yet, the effects on Union citizenship might be more profound. Thus, in this section we draw two principal consequences of the preceding analysis of the link between the abolition of border controls and Union citizenship: At a meta-level, the partial suspension of Schengen affects negatively the way in which citizens relate to the Union and see themselves as Union citizens; at the level of positive law, the link between the abolition of border controls and Union citizenship in the Treaty framework calls for an interpretation of the rules in the Schengen Borders Code on the reintroduction of border controls.
If the reintroduction of border controls is considered from a 'purely' legal perspective of free movement rights of Union citizens, the infringement of these rights appears minimal. Having to flash one's passport at the border is merely a minimal infringement of a Union citizen's free movement rights. From this perspective, the reintroduction of border controls seems like, as some scholars argue, a mere nuisance for citizens walking their dog in their favorite park that stretches across an internal border. 148 Yet, this perspective fails to see the more profound effects of the longue durée reintroduction of border controls on how Union citizens see the Union and the way they conceive themselves as Union citizens. Arendt and Hans Lindahl argue, as discussed above in Part D.II., that territorial boundedness and the concrete actualization of values are constitutive features of a political community and essential for the identity of that community. For Arendt and Lindahl, however, territorial boundedness and the actualization of values are preconditions for political communities to exist. In other words: Arendt and Lindahl make an ontological claim. By contrast, we want to highlight the epistemic aspect of the abolition of border controls, something that neither Arendt nor Lindahl describe. The objective of the White Paper to change the way citizens would see the Union illustrates this epistemic aspect of the abolition of border controls. Cognition, as Edmund Husserl argued, has an intentional structure in that it is always aimed at something outside a person and thus relates to things in the world. 149 Thus, the 146 Innenminister Friedrich will mit einem Veto in Brüssel die Aufnahme von Bulgarien und Rumänien in den Schengen-Raum verhindern, DER SPIEGEL (Mar. 3, 2013). 147 See inter alia, European Parliament, Costs of non-Schengen, supra note 6, at 9; European Parliament, Schengen Border Controls, supra note 6, at 11; European Commission, Schengen Strategy, supra note 6, at 3. experience of space represents one of the constituents of human cognition. At the same time, experienced space has a concrete material dimension. The materiality of border posts, barriers and tollhouses are not merely material objects, but also concepts that have specific meanings: They signify the limits of the political realm and the operation of the law. A transformation of this materiality, for example, the abolition of border controls, thus restructures the meaning of political concepts through everyday lived experiences and changes the way citizens experience the Union: they do not see different Member States separated by border controls, but a single area. Conversely, the longue durée reintroduction of border controls transforms the way citizens relate to the Union. As border controls in the Schengen area become the new normality, citizens might accord priority to national security over free movement within the Schengen area and their sense of Union citizenship, of being part of a broader community of Union citizens that transcends their national community, might dwindle. To bring some empirical bearing on this argument: When asked in a Eurobarometer poll in 2018, more than two-thirds of Union citizens -sixty-eight percent-considered the abolition of border controls one of the main achievements of the Union and more than half of the respondents mentioned that they were aware of the temporary reintroduction of border controls by their Member State. 150 The abolition of controls at internal borders does not mean that the EU, as a legal space, constitutes an abstract and borderless space which, in contrast to Member States' legal orders, is not based on territory. 151 Quite the contrary: The abolition of internal border controls goes hand in hand with the establishment and fortification of a common external border and, thus, constitutes a common bounded space that is more than the mere sum of Member States territories. The abolition of internal border controls thus constitutes an essential element of the EU's territorial claim and EU law's territorial grounding. 152 The second consequence of the preceding analysis on the link between Union citizenship and the abolition of internal border controls concerns the implications for the interpretation of EU law. More precisely, the interpretation of public policy and internal security as derogations from the general principle of the absence of border controls. With prolonged reinstatements of border controls, the Schengen area clearly is in crisis. At the root of this crisis are the security concerns of 150 The views on the Schengen area, however, vary between Member States. While eighty-seven percent in Luxembourg, eighty percent in Poland , eighty percent in Slovakia ,seventy-nine percent in both Lithuania and the Netherlands , as well as seventy-seven percent in both Germany and Greece citizens consider the Schengen area as one of the main achievements of the EU, respondents in the UK were the least likely to agree with that statement with forty-five percent. In the UK there was, however, a high proportion of "don't know" answers with thirty-five percent. Moreover, the absence of passport controls ranks as the single most positive aspect of the Schengen area in the perception of respondents, ahead of easier trade and cross-border travel. See European Commission, Special Eurobarometer 474 Report (Dec. 2018), 39-40, 48, http://www. europeanmigrationlaw.eu/documents/EuroBarometer-Schengen-FullReport.pdf. 151 As argued, for example, by Alain Supiot, who comprehends the EU as space. For him, the EU "no longer defines itself as a single territory or a group of discrete territories" but rather as an "area of freedom, security and justice : : : designed to include an indeterminate and indeterminable number of new member States." Supiot contrasts the legal order of states, which is territorially bound, with the legal order of the EU, which it not territorially bound. Thus, the extending reach of EU law consequently results for Supiot in the "dissolution of the singularity of territories into an abstract, measurable and negotiable space." See Alain Supiot, supra note 56, 390-91. Still, Supiot views the area of freedom, security and justice exclusively in terms of the internal market rules, in other words as a market space, which, as we discussed above, is both historically and normatively unconvincing. 152 This claim of the EU to its "own" territory does not mean that Member States territories are replaced by a common Union territory. Rather, the relation between Union territory and Member States territories is reflexive: Similar to Union citizenship, Union territory depends on and is an accessory to Member territories, yet at the same time modifies the legal meaning and conceptualization of Member States territories. The EU's territorial claim, as Josef Weinzierl points out, does not imitate state territory by claiming ultimate authority over a distinct junk of the earth, but rather opens "national territories and to create a transnational, mutually integrating, and yet bounded space. Member States, or, to be more precise, the view that border controls are an adequate instrument to respond to Member States' concerns of long-term threats, whether perceived or real. In the past two decades, this view changed considerably. While Member States rejected the reintroduction of border controls in the immediate aftermath of 9/11, because the "fight against terrorism would be a long-term activity" and the Schengen Borders Code allows temporary reintroduction of border controls only, 153 since 2015 some Member States are increasingly convinced that border controls represent adequate measures to respond to long-term threats. 154 However, it is not just Member States themselves that advance this view. Even the Commission seems to consider the derogations in the Schengen Borders Code almost exclusively from the perspective of Member States' security concerns.
Yet, if one sees free movement in the internal market and borderless travel in the AFSJ as two sides of the same coin -Union citizenship-, the case for a unified approach towards the concept of public order and public policy is not hard to make. It would mean that the derogations under the Schengen Borders Code are interpreted in line with EU free movement law, subjecting Member States to greater scrutiny, requiring a genuine and sufficiently serious threat to a fundamental interest of society. Although Member States are allowed a margin of discretion in the application of this concept, it is not exempt from judicial review, must be interpreted strictly, and its scope cannot be determined unilaterally without control by the Union institutions. An interpretation of the public policy and internal security exception in line with the case law on Union citizenship, would not only allow for a restoration of borderless travel in Europe, it would also result in a consistent and uniform interpretation of both the AFJS and the internal market objective, doing justice to Union citizenship as the "fundamental status of nationals of the Member States", 155 under both articles.
Although the Court has held that the same language in different legislative instruments does not necessitate the same interpretation, it has on prior occasions interpreted the concepts of public policy in AFSJ legislation applicable to third-country nationals, in the same way as under the Citizenship Rights Directive. 156 The argument that an interpretation in line with the Citizenship Rights Directive is not possible, as it would automatically apply to third-country nationals who do not benefit from the right to free movement, ignores that this is precisely the reason for which rules with regards to external borders have been adopted. To treat third-country nationals differently in this regard would amount to a case of unjustified discrimination. 157 In fact, in the instances in which the Court of Justice has interpreted the concept of public policy or public security differently, the Court was concerned with the interpretation of these exceptions in AFSJ legislation governing the first access of third-country nationals to Union territory. 158 This does leave open the question on how to relate the public policy and public security exception to Article 72 TFEU and Article 4(2) TEU, which state that Member States remain responsible for their own internal and national security. In the internal market, it is standing case law, that where harmonizing measures have been adopted, national legislation is checked against that 153 See Groenendijk, supra note 37, at 166. secondary legislation and a Member State can no longer invoke the Treaty provisions. 159 In a number of recent decisions, the Court of Justice held that Article 72 TFEU cannot be validly invoked when EU secondary law already sufficiently takes into account the security concerns of Member States. Much like the Court has subsumed arguments on national constitutional identity under the public policy exception, the Court limited the possibility to invoke Article 72 TFEU as a self-standing exception. 160 In the infringement case Commission v Poland and Hungary, which concerned the failure to implement Council decisions that aimed at relocating asylum seekers from Italy and Greece to other Member States, Poland, Hungary, and the Czech Republic invoked Article 72 TFEU to justify their non-compliance. In an earlier action for annulment against one of these decisions, Poland had already unsuccessfully argued that the Council decisions violated the principle of proportionality, as it did not allow the Member States to fulfil their obligations under Article 72 TFEU. Here, the Court had answered that the Relocation Decisions allowed for the refusal of a candidate based on public policy or public security concerns. 161 The Court replied, first, that although Member States remain competent to adopt measures to ensure law and order and security on their territory, the adoption of such measures still falls within the scope of Union law: "It cannot be inferred that the Treaty contains an inherent general exception excluding all measures taken for reasons of law and order or public security from the scope of European Union law. As such measures fall within the scope of Union law, the Court is competent to adjudicate on the compatibility of these measures with Union law." 162 In this regard, the Court leaves no doubts that the derogations in Article 72 TEFU refer to "exceptional and clearly defined cases" and must be interpreted strictly. 163 The CJEU made clear that Article 72 TFEU "cannot be read in such a way as to confer on Member States the power to depart from the provisions of the Treaty based on no more than reliance on those responsibilities" 164 and that it precludes Member States from peremptorily invoking Article 72 TFEU "for the sole purposes of general prevention." 165 In Commission v Hungary, another infringement procedure, Article 72 TFEU was invoked once again, this time in conjunction with Article 4(2) TEU. Hungary argued that the large number of persons seeking international protection posed a risk to its public order and internal security, allowing it to depart from EU asylum legislation. The CJEU rebuked that argument as too general, holding that Hungary failed to demonstrate, "to the requisite legal standard," that it was necessary for it to derogate from secondary legislation. 166 The Court emphasized that the legislation in question provided for the specific situation in which Member States are confronted with an exceptionally large number of third-country nationals. The fact that there was a proposal pending to amend these provisions, does not in itself justify the conclusion that the concerns that Article 72 TFEU aims to protect have not been sufficiently taken into account. As regards Article 4(2) TEU, the Court put the bar even higher, requiring that national measures  taken by reference to this article must be necessary to "effectively safeguard[. . .] the essential State functions." 167 It is submitted that the provisions of the Schengen Borders Code take sufficient account of the Member States internal security concerns. Member States can unilaterally reintroduce controls for a maximum period of eight months. Articles 25-28 Schengen Borders Code. For the specifically serious threats provoked by systemic deficiencies in the management of the external borders, Article 29 Schengen Border Code provides an answer. More importantly, the Council already considered that temporary border controls do not constitute adequate measures to respond to threats of a prolonged nature. 168 To interpret Article 72 TFEU any differently would, as the Court held in Commission v Poland and Hungary, "impair the binding nature of European Union law and its uniform application." 169 Only in the most of exceptional of circumstances affecting the Member States' powers to ensure internal security recourse can be had to Article 72 TFEU and Article 4(2) TEU. Such a reading is in line with Advocate General Jacobs' interpretation of that other derogation clause in primary law: The internal market emergency clause in Article 347 TFEU. Advocate General Jacobs argued that "serious internal disturbances affecting the maintenance of law and order" would necessarily entail "a breakdown of public order on a scale much vaster than the type of civil unrest which might justify recourse to Article 30 TFEU." 170 Recent case law supports a similar reading of Article 4(2) TEU.
In Quadrature du Net, the Court of Justice interpreted the objective of safeguarding national security (Article 72 TFEU) in light of Article 4(2) TEU. The Court stated that Article 4(2) TEU refers to the Member States' "primary interest in protecting the essential functions of the State and the fundamental interests of society and encompasses the prevention and punishment of activities capable of seriously destabilizing the fundamental constitutional, political, economic or social structures of a country and, in particular, of directly threatening society, the population or the State itself, such as terrorist activities." 171 The Court argued that this went beyond the objectives safeguarding public security in the secondary legislation at issue, the e-privacy Directive -Directive 2002/58. Threats to national security, the Court of Justice argued, would be distinct "by their nature and particular seriousness, from the general risk that tensions or disturbances, even of a serious nature, affecting public security." 172 Only in such circumstances can threats to national security justify measures that are more far-reaching than normally permitted by secondary legislation. 173 These measures, however, still need to comply with the basic criteria set forth in Article 52 of the EU Charter on Fundamental Rights. Although in this case the question evolved around the safeguarding of a fundamental right, a similar interpretation must apply to a limitation of the right to move freely across internal borders of Union citizens.

F. Conclusions
In this Article we argued that the rules on the absence of border controls and Union citizenship are closely connected and must be considered together. The history of the abolition of border controls shows that the objective of the abolition of border controls was not merely to further economic 167 Id. para 262. 168 See Groenendijk, supra note 327, at 166. 169 Commission v Poland and others, C-715/17, at para. 143. 170 Opinion of Advocate General Jacobs at para. 47, Case C-120/94, Commission of the European Communities ν. Hellenic Republic (April 6, 1995). 171 Joined Cases C-511/18, C-512/18 & C-520/18, La Quadrature du Net and Others v. Premier ministre and Others, ECLI: EU:C:2020:791, Judgment of 6 Oct. 2020, para. 135. 172 Id. at para. 136. 173 Id.
integration, but also to foster a European political identity. Key policy documents from the 1980s show that the abolition of physical border controls was considered crucial in transforming the way citizens relate to the Union. The current Treaty framework formally links Union citizenship to an area without internal border controls where Union citizens can move freely. Thus, the rules on Union citizenship and the Schengen acquis are quite clear: Union citizens have, in principle, a right to move freely across internal borders without being subject to border controls.
Yet, present day reality stands in stark contrast to the development and the current state of Union law as discussed in this Article. Long gone are the days in which the Commission criticized border controls as an impediment to the "broader and deeper Community envisaged by the original Treaties" and an "outward sign of an arbitrary administrative power [by Member States] over individuals and as an affront to the principle of freedom of movement within a single community." 174 Despite President von der Leyen calling Schengen the linchpin for fully restoring the four freedoms, 175 both the tone and (in)action of the Commission point in the opposite direction. Commissioner Johansson recently remarked at the Second Schengen Forum that she does "not intend to remove the unilateral right of Member States to introduce internal border checks when that is indeed necessary and justified as measures of last resort against a concrete threat," which was confirmed in the Commission's new strategy for Schengen. 176 Despite the connection of the Schengen acquis with citizenship rights and the strict conditions on reintroducing border controls in the current Treaty framework, current practice emaciates these strict conditions and gives undue room to the sovereignty concerns of Member States, couched in security terminology. Not only does this wrongfully consider border controls as an adequate measure to tackle long-term security threats, which is doubtful in itself; more importantly, it undermines one of the core achievements of European integration of the last three decades-an area without internal border controls in which Union citizens can move freely. Moreover, it risks changing the understanding of citizens as Union citizens. The construction of the area without internal frontiers was not an exclusively top-down process driven by political elites, as the literature on Schengen describes it. The legal construction of the area without internal border controls was also driven by citizens and remains so till this day. 177 Examples of citizens asserting their free movement rights as Union citizens include, for instance: The protests and road blockages by truck drivers against border controls in the 1980s that eventually resulted in the conclusion of the Saarbrücken agreement; the strategic litigation of Members of the European Parliament to get rid of border controls in the Wijsenbeek case in the 1990s; 178 and cases that are currently pending before the Court of Justice. 179 Although it is cause for hope that the Commission's new Schengen Strategy acknowledges that Schengen is a symbol of Europe's interconnectedness and the ties between the peoples of Europe, it requires an interpretation of the Schengen rules in line with the Treaties' objectives and origins 174 Commission White Paper, supra note 11, paras. 24, 47-48. 175 to more forcefully protect borderless travel in Europe. It is time to draw the conclusion from the incorporation of Schengen into the EU legal framework and to give full effect to Union citizenship some twenty years after its establishment. To think that the establishment of the internal market was any less controversial or politically sensitive, is historically wrong. It was the Commission, backed by a Court determined to give full effect to the Treaties, that allowed for the success of the Single Market project. Let it take an equally principled role in the protection of the Schengen area and citizens' rights. Failing to do so, it will once more be up to the Court of Justice to ensure the full effect of Union law and protect the rights of Union citizens under the treaties. This time, however, it is not so much about establishing those rights, as about protecting the achievements of Schengen and the rights of Union citizens.