It was a turning point in the history of European integration and a unique moment for the first President of the European Commission, Walter Hallstein. On 16 June 1965 in the afternoon, Hallstein appeared before the European Parliament (EP) to express his strong support for the constitutional interpretation of European lawFootnote ¹ launched by the European Court of Justice (ECJ)Footnote ² in the new Van Gend en Loos (1963) and Costa v ENEL (1964) judgments.Footnote ³ Here the ECJ had controversially assumed the competence to define the relationship between European law and national constitutional orders. By doing so the ECJ sidestepped the respective constitutional clauses of the member states on how to receive international (and European) law. Primary legal norms from the founding treaties, when clear and unambiguous, would have direct effect inside the legal order of the member states as well as primacy vis-à-vis national legislation, whether precedent or antecedent. This was a remarkable breakthrough for a constitutional interpretation of European law.Footnote ⁴ However, in the cautious terminology of the Court, it merely signified the emergence of a ‘new legal order’.Footnote ⁵

Hallstein had long supported a constitutional basis for the European construction.Footnote ⁶ Already, when he led the West German delegations negotiating the Treaty of Paris (1950–1951) and the two Treaties of Rome (1955–1957), his ambition had been to create a federal Europe based on a genuine European constitution.Footnote ⁷ This was also a key part of his agenda as President of the European Commission of the European Economic Community (EEC)Footnote ⁸ from 1958, despite the limited results that had been achieved in this direction when negotiating the founding treaties.Footnote ⁹ To Hallstein, as he explained to an academic audience at the University of Padua in March 1962, it was crucial that the European Communities (EC) created a legal order that ‘replaced violence and political pressure with the rule of law in the relations between the member states’.Footnote ¹⁰ Hallstein wanted a European version of the old mantra of international law: peace through law.

In his speech before the EP in June 1965, Hallstein concluded that the relationship between the legal order of the EC and national constitutional orders was of major political importance. It was in fact an existential question on which the establishment and implementation of the Common Market depended. A question, according to Hallstein, which required an answer based on legal methods. Not only had the ECJ now provided the right solution; the EP and the report produced on the matter by its legal committee also backed the new constitutional interpretation of European law.Footnote ¹¹ A key objective of the Hallstein Commission had thus been achieved.

Until now Hallstein’s speech has been overlooked by historians of European integration, who have instead understandably focused on the so-called ‘Empty Chair Crisis’ that broke out two weeks later.Footnote ¹² During this crisis, French President Charles de Gaulle and his government boycotted the Council of Ministers until January 1966, and demanded a complete overhaul of the institutional system of the EC to reduce the independence of the supranational institutions and force the dismissal of the activist Hallstein Commission. The crisis was eventually resolved with the Luxembourg Compromise that introduced an informal veto right for the member states in the legislative process.Footnote ¹³ However, while the veto right gradually lost its original legitimacy in the 1980s with the introduction of the Single European Act, the constitutional interpretation of European law had come to stay and arguably remains one of the most lasting achievements of the Hallstein Commission. A legal revolutionFootnote ¹⁴ had been born that would deeply shape the future of the EC. It was, however, far from complete. The breakthrough for a constitutional interpretation of European law may have been a crucial turning point in the early struggle over the institutional and political nature of European integration. But the political and legal battle over the development of a broader constitutional practice would continue until the establishment of the European Union (EU) in 1993.

This book explores the history of the battle over the constitutional practice of European law from 1950 to 1993. It offers the first archive-based history of what constitutes an important, yet still relatively unknown slice of European integration history. In the first half of the book, the role of the EC institutions as well as the transnational networks of European law scholarship will be explored. In the second half, the reception of the constitutional practice of European law in the member states will be analysed through the examples of West Germany, France, the Netherlands and Denmark. Altogether, the book offers a new revisionist historical interpretation of how European law evolved from 1950 to 1993. It argues that during this period European constitutionalism developed as a doctrinal and discursive practice of the ECJ, the Commission, the EP and European legal scholarship. This practice was, however, generally resisted and accepted only in a piecemeal fashion by national governments, administrations and courts until the mid-1980s. The Single European Act of 1986 forced the member states to participate more fully in the mechanisms of the legal order built by the ECJ because it underpinned the Single Market project coveted by the governments. However, during the negotiations on the Maastricht Treaty, a majority of member states, supported in parallel by a number of constitutional and high courts, nevertheless rejected to accept the constitutional practice as a key legitimating principle of the new EU.

Law and Politics Studies in Context

Although historians had overlooked the importance of law to the history of European integration until the last decade,Footnote ¹⁵ this was certainly not the case with the social sciences. Legal scholars have long researched and debated the nature of European law and its role in the integration process, and from the 1990s, first political science and then sociology also entered the fray. Which theories and interpretations of the development of European law from 1950 to 1993 did these disciplines produce? Interestingly, they tell essentially the same story, albeit with some variation. The essence is that European law was successfully constitutionalised by the ECJ. Through its case law the Court gradually transformed the Treaties of Rome into a proto-federal constitution. This development was eventually, it is furthermore argued, accepted by the member states. The EU, established in 1993, was consequently built on a European rule of law and European politics had been judicialised to the extent where European law would frame and at times even decide policy making.Footnote ¹⁶

Before discussing the different variations of this core narrative of successful constitutionalisation, let us first explore where the notion came from originally. The claim that European law had been constitutionalised first entered academic discourse with the publication of a now famous article by an American legal scholar, Eric Stein, in 1981.Footnote ¹⁷ From the legal revolution in the early 1960s to 1980, legal scholarship on European law, to a large extent dominated by members of the ECJ or the Commission,Footnote ¹⁸ had employed the discreet and bland vocabulary of ‘new legal order’ invented by the court. This scholarship focused on functional analyses of European law and generally avoided debates on what constituted the nature of ‘the new legal order’. If challenged, judges such as Pierre Pescatore from Luxembourg or Dutch André Donner chose a defensive stance, pointing out that the ECJ had simply drawn out the legal consequences of the Treaties of Rome and established a European rule of law (Article 164 of the European Economic Community Treaty (EEC Treaty)).Footnote ¹⁹ In this largely European debate, Stein, as a professor at the University of Michigan Law School at Ann Arbor, represented an outlier position. Stein did not shy away from a much more political interpretation of the nature of European law. Shaped by his experience as a Jewish refugee from Czechoslovakia before the war, he had witnessed most of his family perish in the Holocaust, and consequently developed a strong ideological belief in the importance of European unification.Footnote ²⁰ Drawing by analogy on the American federal experience, by 1965, he already characterised the Van Gend en Loos and Costa v ENEL judgments as a constitutional breakthrough, where the ECJ had interpreted the treaties as if they were of a constitutional nature and rejected ‘public international law as rationale for its power’.Footnote ²¹ Stein would defend this view with ideological zeal, and criticised other legal scholars behind the scenes, if they did not understand the political necessity of creating an autonomous European legal order. This was the case for example with the young Belgian scholar and lawyer Michel Waelbroeck, who considered the Costa v ENEL judgment to be quite a scandal because the ECJ had assumed the competence to replace the constitutional clauses of the member states on the reception of international law with its own system. In a forceful letter, Stein insisted that it was absolutely essential for the younger generation of scholars to support a progressive development of European law and not stay prisoners of ‘their own national constitutional concepts grounded in German positivism’.Footnote ²² Despite his activism, Stein’s views had little impact on the European legal debate before the 1980s.

His famous article from 1981 was first presented in a draft at a conference of the American Society of International Law in April 1978. Here he admitted that the paper title, ‘The Emerging European Constitution’, was ‘unrealistic and Pollyannaish, if not outright propagandistic’.Footnote ²³ However, this time his interpretation was finally picked up in Europe. At the Department of Law at the new European University Institute (EUI), Italian Professor Mauro Cappelletti was about to embark on a grand new research project entitled ‘Integration through Law’ that compared the American federal experience with the process of European integration, repeating an exercise already done by Stein in a conference in Bellagio at Lake Como in 1979.Footnote ²⁴ The project, coordinated by an unknown, young, but very talented Israeli doctoral student, Joseph H. H. Weiler, who would quickly be promoted to professor, was of an entirely different scale, however. It involved a host of academics and practitioners and was closely coordinated with both the ECJ and the Legal Service of the Commission. Although published in a now classical multi-volume series in green cloth, it was arguably Weiler’s own ambitious scholarship that laid the groundwork for the breakthrough of the thesis of considering the development of European law as one of successful constitutionalisation.Footnote ²⁵

Building on Stein, Weiler argued that the ECJ had constitutionalised the Treaties of Rome by creating a binding legal order with directly effective legal norms supported by strong enforcement mechanisms such as the preliminary reference mechanism (Article 177 of the EEC Treaty), whereby private litigants and their lawyers could call on the national courts to ask the ECJ for advice with regard to the implementation of European law in member states. National governments accepted this development because the Luxembourg Compromise had granted the member states a veto right in the legislative process that counterbalanced the progressive tightening of the legal obligations of the EC. This nexus – Weiler did not necessarily believe there was a direct causal link between the two developments – was, however, broken by the Single European Act of 1986 that finally reintroduced majority voting in the legislative process to establish the new Single Market. He therefore predicted that national governments in response might curb the powers of the ECJ and limit judicial influence in the integration process.Footnote ²⁶ Weiler’s scholarship coincided with the revival of the EC in the second half of the 1980s and the strong institutional and political dynamics that appeared around the creation of the Single European Market. In this context, Weiler was propelled to academic stardom and his interpretation that European law had experienced a successful constitutionalisation entered the mainstream of the new broader field of European studies, which evolved from the late 1980s to explain the new dynamics of European integration at the end of the Cold War.

With Weiler as the most influential legal scholar in the broader field of European studies in the early 1990s, and the apparent successful role of European law as a remarkable feature of the new dynamics of European integration, it was perhaps predictable that the new generation of young American political scientists adopted the constitutionalisation thesis as the foundation for their own work on European law.Footnote ²⁷ This new political science literature on European law first repeated the theoretical debates within their own field.Footnote ²⁸ However, soon a group of young political scientists began to explore empirically how the constitutionalisation of European law had actually taken place, using new innovative theoretical and empirical approaches. Competing explanations emerged. By means of quantitative research on litigation, Alec Stone Sweet and Thomas L. Brunell argued that a self-sustaining dynamic had driven constitutionalisation and constituted a veritable motor of integration. European firms started a virtuous circle of trade liberalisation and legal integration through litigation before national courts, which then sent questions to the ECJ in Luxembourg by way of the preliminary reference mechanism. The case law of the ECJ that generally favoured trade liberalisation was then subsequently codified by Council legislation which in turn, facilitated more litigation.Footnote ²⁹ To Stone Sweet and R. Daniel Kelemen, ‘integration through law’ provided a dynamic strong enough to overcome the backlash from the member states predicted by Weiler. Consequently, ‘constitutionalisation’ led to a comprehensive judicialisation of the European Union.Footnote ³⁰

The question was now whether the self-sustaining mechanism theorised by Stone Sweet and Brunell on the basis of quantitative studies could be identified by qualitative empirical research.Footnote ³¹ This turned out not to be the case, when Karen Alter worked her way through the West German and French cases from 1950 to 1993. Based on interviews and publicly available sources, her understanding of the dynamics of the process of constitutionalisation turned out very differently. She concluded that the constitutionalisation of European law had rather been driven by lower national courts working in tandem with the ECJ. She also demonstrated how complex and conflictual the process actually was due to the widespread resistance in the member states, in particular from national courts of last resort and parts of the administrative and political elite. Her overall conclusion was nevertheless in line with the mainstream view that by the early 1990s constitutionalisation had been successful and a European rule of law established.Footnote ³² However, for all the great qualities of Karen Alter’s account of the West German and French battles over the constitutional practice, its empirical foundations was limited to interviews and public sources. It was Alter’s book that provided the direct inspiration for the doctoral research of one of the editors of this book.Footnote ³³ This book will consequently move significantly beyond the state of the art due to its use of systematic archival research.

With Stone Sweet, Brunel and Alter confirming, although with alternative explanations, that European law had indeed been successfully constitutionalised, law and politics studies from the 2000s onwards began to focus on the contemporary role of the Court of Justice of the European Union (CJEU) and European law in the EU. New research attempted to refine what role the CJEU played in the policy-making process of the EU and focused on the extent the Court had been subject of critique.Footnote ³⁴ Other strands of research led to an improved understanding of the reception of national administrations both of European legislation and CJEU case law.Footnote ³⁵ While the field of law and politics studies have thus increased in sophistication over the last decades, researchers of the field did not return to re-examine the original understanding of how European law had been constitutionalised between 1950 and 1993.

Only very recently have two political scientists turned their attention to the period from 1950 to 1993. Tomasso Pavone has explored the role of the so-called Euro-lawyers from the 1960s to the 1980s, who out of ideological zeal and professional self-interest were crucial in producing a significant number of the cases that came through the ECJ’s preliminary reference system during this period. Pavone’s pathbreaking empirical results, which are based on interviews, as well as research in the archive of the CJEU, align very well with the results of the historical research in this volume. Another interesting contribution has come from William Phelan, who has explored the contribution of French politician and ECJ judge, Robert Lecourt, by analysing his legal writings since the interwar period and key judgments around the legal revolution in the first half of the 1960s.Footnote ³⁶ From the perspective of the discipline of history, Phelan’s work is perhaps somewhat limited by the lack of archival research, which might have produced a richer understanding of the personality of Lecourt and the historical context in which he worked.Footnote ³⁷ However, Phelan manages nevertheless to re-interpret and nuance the doctrinal development around the legal revolution. The historical interest and pioneering contributions of Pavone and Phelan is a most promising new development that this book hopes to encourage further.

In the last two decades, a school of sociological research inspired by Pierre Bourdieu on the role of jurists and legal techniques in the European construction has also made an important contribution to the understanding of the history of European law from 1950 to 1993.Footnote ³⁸ The sociological research has offered important new theoretical and empirical nuance in the analysis of the role of jurists, the legal profession, and the supranational institutions. The extent to which jurists had multiple roles in and outside European institutions, the mixture between politics and law and the blurring of the boundaries between European law academia and the supranational institutions are important insights that has inspired the work of this book. Most of the empirical studies conducted by sociologists have also included a historical dimension, which have contributed to our historical understanding of how European law has developed.Footnote ³⁹ Nevertheless, seen from the approach developed in this book, the sociological literature is limited in two ways. Just as in political science, the alleged successful constitutionalisation of European law has not been questioned. Instead, sociological research has considered constitutionalisation the key process through which jurists in and outside the European construction have empowered both the supranational institutions and their own profession. Second, the strict Bourdieusian approach, the relatively narrow focus on the role of jurists and the supranational institutions and the lack of systematic archival research have tended to skew the empirical results produced.Footnote ⁴⁰ As a result, the overall understanding of the development of European law ends up lopsided with an overwhelming focus on the supranational institutions, their autonomy and power. What is missing in the account is the role of the European Council/Council of Ministers, as well as in-depth analyses of the responses by national governments, administrations and courts in the battle over European law.Footnote ⁴¹

We must turn to recent legal scholarship to identify the first critical voices that question the mainstream interpretation.The new history of the legal dimension of the EU written by the German legal scholar Frank Schorkopf certainly offers a more balanced account of the broad developments from 1948 to 2007.Footnote ⁴² Schorkopf employs a multidimensional approach to the history of European law, which argues that the overall institutional frame of the European construction was decided by competing and complementary ideational positions: constitutionalism, intergovernmentalism and pragmatism. In this way he goes significantly beyond the mainstream interpretation’s narrow focus on constitutionalisation and contextualises and nuances our understanding of the history of European law. His monograph thus stands as an excellent synthesis of existing research, including also the archive-based legal histories produced over the last decade by the contributors to this book. At the same time the approach of Schorkopf’s book produces certain unfortunate limitations. First, while the ideational positions outlined capture most of the various institutional and political debates, the approach arguably tend to delude and even sidestep the core political conflict over the institutional and legal shape of the European construction between national governments unwilling to furnish the European construction with autonomous power and European federalists and constitutionalists that aimed exactly to do that.Footnote ⁴³ Second, by employing a constitutional framework informed by the century long history of western constitutions, Schorkopf inadvertently ends up writing the legal history of the EU with the vocabulary of those political forces who strove for a European federal constitution. The great advantage of the approach is that it allows Schorkopf to author a book that directly contributes to the democratic debate of the contemporary EU using the constitutional approach as a yardstick for clarifying the status of the Union. The disadvantage is that his constitutional approach seriously skews our conceptual lenses and thus our understanding of how the battle over the legal dimension of the European construction has played out. This book instead introduces an open-ended approach that does not predefine the nature of the historical process explored.

In comparison to Schorkopf, the decade-old book of American legal scholar Peter Lindseth, Power and Legitimacy, had more critical bite regarding the dominant constitutional paradigm of European law.Footnote ⁴⁴ In his attack against the paradigm, Lindseth argued that European law had deep roots in the post-war administrative state of the member states. In fact, since 1958, European law had converged around the legitimating structures and normative principles of the post-war constitutional settlement of the administrative state. These include the delegation of responsibilities to independent agencies such as the Commission or the ECJ, combined with the collective oversight by the Council of Ministers. Although Lindseth’s work illuminated the parallels between the rise of the administrative state and the way the EC has developed, his focus on the administrative roots of European law meant that he largely ignored how central the battle over the constitutional practice was to the broader development of European law from 1950 to 1993. The result amounts to an unbalanced account of the history of European law that may question the success of European constitutionalism but does so without exploring how precisely the latter failed.Footnote ⁴⁵

Conceptual contributions of legal scholars debating the nature of constitutionalism have also proved useful in the context of this book. The core question is what does it take for a political entity – a state or an international entity such as the EU – to obtain constitutional status? Here disagreement exists between legal scholars. One position promoted by the prominent scholar of German constitutional law, Dieter Grimm, argues that the EU is not fully constitutional because it has not experienced a constitutional moment, wherein it obtains popular endorsement. After all, the Constitutional Treaty was rejected by both the electorates of France and the Netherlands in two referenda in 2005. According to Grimm, it is thus fairly simple to ascertain whether a political entity has constitutional legitimacy or not. However, what if constitutional legitimacy could be constructed and obtained over time in a historical process, as argued by Finnish scholar Klaus Tuori?Footnote ⁴⁶ What would it take for the EC to pass the threshold and obtain full constitutional legitimacy in the absence of popular assent? Would it be enough if the CJEU has developed a proto-federal legal order based on a constitutional interpretation combined with a constitutional discourse backed by key institutions and important social actors? Lindseth believes that no, this is not sufficient to replace a constitutional moment with explicit popular endorsement. In his view, for the EU to obtain genuine constitutional legitimacy, it would also need genuine political autonomy. This is clearly not (yet) the case with the EU today, which despite its independent supranational institutions remains dominated by the member state governments collectively in the European Council. Nor is the EU currently able systematically ‘to mobilise fiscal and human resources for collective ends in a compulsory and legitimate fashion’. Even if the first European lending in international markets during the pandemic offered a first example of how it can be done.Footnote ⁴⁷ In a European context another serious obstacle may well exist to a smooth process of constitutionalisation. The member states of the EU have well-established, and sometimes centuries-old, political and legal cultures that situate constitutional legitimacy firmly in a national context, closely intertwined with national identity.Footnote ⁴⁸ Compared to the American states around and in the decades following the American revolution, the national constitutions of EU member states are thus much more entrenched. In this context, it is difficult to see how a constitutional breakthrough for the EU can happen without a formal constitutional moment that includes popular endorsement.Footnote ⁴⁹

This book argues that although a constitutional practice evolved in European law from the early 1960s to 1993, including the gradual establishment of a proto-federal European legal order and an accompanying constitutional discourse supported by the supranational institutions and European law academia, European constitutionalism ultimately did not become the key legitimating principle underlying the Maastricht Treaty nor was it accepted by national judiciaries. Not only did the new treaty not present a ‘constitutional moment’, but it also formalised a consolidation of the collective power of national governments to run the new EU through the European Council and for national judiciaries to place conditions on the future course of European policy. This book thus argues, in contrast to the mainstream interpretation of the development of European law discussed above, that European constitutionalism failed to obtain a major breakthrough in the early 1990s.

Historiography and Methodology

As the first archive based history of European law from 1950 to 1993, this book draws on and contributes to a number of new trends in the historiography of European integration.Footnote ⁵⁰ From the late 1970s to 2000, historiography was largely dominated by either a focus on the role of European federalism or European identities in the integration processFootnote ⁵¹ or analyses of how the European states pursued security, commercial and economic interests by the means of European integration.Footnote ⁵² However, in the last two decades we have seen the gradual establishment of several new approaches and a broadening of topics explored. This includes archive-based research on the history of the supranational institutions,Footnote ⁵³ including their administrative history, which have demonstrated their independent role as agenda setters with the ability to influence European policy making.Footnote ⁵⁴ In addition, historians have also now explored how transnational networks and societal actors have shaped and underpinned the integration process.Footnote ⁵⁵ A broad range of policy fields have been explored in depth such as for example the Common Agricultural Policy,Footnote ⁵⁶ the Common Market,Footnote ⁵⁷ the Common Commercial Policy,Footnote ⁵⁸ the external policy versus former colonies,Footnote ⁵⁹ monetary policy,Footnote ⁶⁰ social policy,Footnote ⁶¹ environmental policyFootnote ⁶² and cultural policy.Footnote ⁶³ Finally, the historians behind this volume have produced a significant body of research on the history of European law focusing in particular on the 1950s and 1960s.Footnote ⁶⁴ Historians today thus conceive of European integration as being developed in a complex political and institutional process involving not only the member states, but also the far from powerless supranational institutions, underpinned by transnational networks and interested societal actors.Footnote ⁶⁵ The history of European law from 1950 to 1993 analysed in this book only reinforces this understanding by highlighting how the supranational institutions, supported by European law academia, attempted to develop the EC in a constitutional, and even federal direction. Even if this alliance was ultimately unsuccessful in the early 1990s, as our book argues, its actions greatly shaped the development of European law in the period analysed.

The book also connects to another important trend in the historiography of European integration, although in a more indirect manner. In several publications, Kiran Patel and Wolfram Kaiser have attempted to ‘provincialise’ European integration. First, they have argued that the EC was but one example among others of international cooperation after 1945 and only gained a more central status in the 1980s. Second, they have pointed out that European integration did not constitute a clear break with the interwar period, as typically claimed both by the European institutions and historians of European integration.Footnote ⁶⁶ With regard to the history of European law, Patel has argued along similar lines by emphasising that European law did not originally differ significantly from international law; it was instead the self-fashioned constitutional claim that over time would help differentiate the EC from other international organisations.Footnote ⁶⁷ The attempts to de-essentialise the history of European integration and integrate it within the broader historiographies of twentieth-century Europe and international history raises an important and fruitful agenda.

To fulfil its promise, however, it requires a solid empirical understanding of the multiple dimensions of European integration that are connected to the broader international context as well as the interwar period. In a new and relatively unexplored part of European integration history such as European law, this book offers for a first, solid archive-based empirical analysis by prioritising an internal European perspective that allows for an in-depth focus on both the European institutions and transnational European law academia, as well as a handful of crucial national histories. Nevertheless, there are without doubt several interesting roads that future researchers can take when connecting the constitutional battle over European law explored in this book to a broader international and temporal perspective. These range from studies of federalisation in a comparative perspective, comparing European integration to the United States of the nineteenth century and the German Zollverein, the links between European law and international law and finally the comparison between the legal dimensions of the EC and other international organisations.Footnote ⁶⁸ This book offers a solid empirical starting point for such future exercises.

The inspiration from the institutional and transnational trends in European integration historiography is also reflected in the way we have approached the history of European law. The methodology employed in this book comes from political history. The aim is to offer an empirically rich and well contextualised history of European law, a history that focuses on the actual social practice that shaped European law and how it connected to the broader political and institutional history of European integration. To do this, we have systematically worked our way through all the relevant archives we could find, ranging from the archives from the European institutions to national archives in more than ten countries and more than fifty private archives, to identify primary sources. This archival methodology stands in sharp contrast with the political scientists and sociologists, cited above, who have used one or two archives in their research. Using only a few archives created a serious methodological problem because all archives have a bias created by the institutions or persons that collected and curated the collection. Archives thus reflect the production of knowledge within an institution at the time and arguably constitutes a discursive sediment of power.Footnote ⁶⁹ However, by systematically exploring all archives deemed relevant to a particular historical problematique, it is possible to introduce different perspectives on the topic at hand which allow the researcher to rigorously check the validity and reliability of their empirical analysis. An effort to explore relevant archival documentation is particularly important to the writing of legal history. The production of European law typically takes place in a black box, in closed meetings of courts and other institutions, administrative processes or networks. This black box is not accessible through public sources because the authority of law is partly based on the claim that law and politics constitute separate spheres, a claim that necessitates an element of cover-up of the social roots of law.Footnote ⁷⁰ Only by identifying the paper trail of such meetings, networks and processes, can we enter the black box where law is produced. What we lay bare in this book, consequently, is how the social practice that produced European law was not only shaped by legal doctrines and arguments, but also by personal motives, ideology, culture, institutional and political interests.

The methodology outlined here differs from most classical scholarship of the history of international law as well as the new intellectual history of international law that has been pursued by legal scholars over the last two decades. Classical histories of international law have typically focused relatively narrowly on doctrinal history and been based on public sources and written law.Footnote ⁷¹ Beginning in the 1990s, a new school of intellectual history of international law, inspired by Quinton Skinner’s Cambridge School of intellectual history, emerged around the former Finnish diplomat and eminent legal scholar Martti Koskenniemi and the Journal of the History of International Law.Footnote ⁷² This new intellectual history has revolutionised our understanding of the doctrinal and intellectual development of international law from 1870 onwards. However, most of its contributions are generally not based on systematic archival research.Footnote ⁷³ Instead, over the last decade, and in parallel with our work on the history of European law, mainstream historians have begun to change the state of the art of the legal history of international law, placing it within its broader societal context and doing so on basis of systematic archival work.Footnote ⁷⁴ In this way, accidentally, our approach to the history of European law over the last decade, borrowed from political history, now appears to be at the very cutting edge of the broader field of legal history of international law.

Finally, a word on the history of European law as a new field of legal history. It is no accident that the discipline of European law has not yet developed a proper legal history taught at European and international universities. First, European law is a relatively young academic discipline and only consolidated in most member states from the 1990s onwards. At the same time, many legal historians worked, as mentioned above, on much older legal history until the 1990s, and those who did work on the history of international law generally had little interest in the variant that developed as part of the process of European integration from the 1950s onwards. Second, and equally important, the academic field of European law has always been deeply politicised due to its origins and continued proximity to those political European institutions. As a result, there has perhaps been a certain reluctance among some legal scholars to dig deep into the history of European law to avoid exposing the role of the academic discipline in promoting the constitutional practice of European law.Footnote ⁷⁵ Recently this trend has been reversed with a new interest of legal scholars in the history of European law and in collaborating with historians and social scientists in order to explore it. The successful EU Law Stories published in 2017 spearheaded this new trend, but other recent publications have further contributed to a what now looks like a new wave of new legal and social scholarship interested in history.Footnote ⁷⁶ We hope this book can further stimulate the interest of lawyers and social scientists in the legal history of European law by offering a general historical synthesis of the development of European law from 1950 to 1993 and new in-depth archive-based case studies of key actors and member states.

Towards a New Historical Interpretation of the History of European Law, 1950 to 1993

The historical interpretation offered by this book is revisionist and presents a genuinely new understanding of the history of European law from 1950 to 1993. Let us conclude this introduction by presenting this new interpretation while placing the contribution of each chapter within its broader framework.Footnote ⁷⁷ First, however, we must carefully consider the approach employed to interpret the history of European law. We contend that by interpreting the history of European law as a successful process of constitutionalisation, or as in the case of Schorkopf as a constitutional history, researchers inadvertently tend to prioritise the perspective of the political forces that promoted European constitutionalism. A constitutional approach and terminology thus impose conceptual limitations on our understanding of the battle over the institutional and legal nature of the EC/EU.Footnote ⁷⁸ To avoid this, we approach the history of European law as a unique historical process that is best analysed as open-ended or sui generis. Here the first task of the historian is to empirically describe and analyse the political and legal institutions and actors involved in battling over the nature of European law and what kind of broader societal processes shaped the development of European law, without taking our starting point from a specific theoretical framework that predetermine the analysis.

What our empirical research demonstrates is that a ‘constitutional practice’ developed in the field of European law from the early 1960s onwards, first as a breakthrough for a constitutional interpretation of the Treaties of Rome and European law, and later as an accompanying legitimating constitutional discourse performed primarily by the supranational institutions and European law academia. Instead of conflating this phenomenon with the overall development of European law, we will throughout the book use the term ‘constitutional practice’ to describe the concrete efforts of the institutions and actors that promote European constitutionalism.Footnote ⁷⁹

The term ‘constitutional’ is chosen despite its ambiguous meaning in different national legal traditions because the historical phenomenon, we explore, was associated with the political ideology of European federalism, based on a constitutional foundation, which emerged in Europe from the 1940s onwards. As the prospect and popularity of European federalism began to fade in the mid-1950s, after the defeat of the European Defence Community and the European Political Community, the potential constitutionality of the European law produced by the European Coal and Steel Community (ECSC) was instead described by legal scholars and practitioners with a different terminology such as ‘supranational’ (early 1950s), ‘autonomous’ (from the last half of 1950s onwards) and finally in the context of the EC ‘new legal order’ (1963–1964 onwards).Footnote ⁸⁰ We do not claim that these alternating terms were completely identical with the original term ‘constitutional’ in all legal implications, nor for that sake that lawyers using these terms were always die-hard federalists. However, the new terminology did reflect a continued wish of the actors using them to position European law closer to state law than international law and thus lay the foundation for a future reform of the EC that would increase its political autonomy from the member states. In the 1980s, the term ‘constitutional’ to describe the nature of European law was finally reintroduced by a strand of legal academia. This old term was readily adopted by the supranational institutions, including the ECJ and European law academia. To conclude, we use ‘constitutional’ to characterise the legal practice we have identified because it most precisely clarifies the ideological links to European federalism that the alternative terminology was meant to obscure.

The term practice is chosen to describe the policies and actions of institutional and individual actors. We argue that the constitutional practice had at least two major elements. The first was the constitutional interpretation introduced and promoted by the ECJ (and the two other supranational institutions) from 1963 onwards and which the court gradually used through its case law to develop a proto-federal European legal order. The second element consisted of a legitimating constitutional discourse from part of European law academia and among the supranational institutions. These two elements evolved over time but merged together in the last half of the 1980s into a genuine European constitutionalism that the member states during the Maastricht Treaty negotiations had the option to based the European Union on.

The historical interpretation comes in two intertwined parts that is reflected in the composition of the book. The first part of the book argues that a constitutional practice developed in European law from the early 1960s onwards promoted by an alliance of the three supranational institutions, the court, commission and parliament and the emerging field of European law academia. In the Chapters 1, 2 and 3, we trace how the supranational institutions produced a breakthrough for a constitutional interpretation of European law with the judgments of Van Gend en Loos and Costa v ENEL in 1963 and 1964 respectively.Footnote ⁸¹ The motives of the key actors involved in the three institutions were an ambition to promote European federalism while simultaneously empowering the supranational institutions vis-à-vis the member states. Although the Empty Chair Crisis and the Luxembourg Compromise fatally weakened the Hallstein Commission in 1965–1966, the constitutional interpretation of European law was not rolled back by national governments. In fact, it grew over time into a broader constitutional practice. With the consolidation of a majority inside the court favouring a constitutional interpretation from 1967 onwards, as shown in Chapter 1, the ECJ continued to build a proto-federal constitutional order through its case law in the 1970s and 1980s. The constitutional interpretation of European law was backed and legitimised both by the Commission and the EP, but also from part of European law academia, as demonstrated in detail in Chapters 2, 3 and 4. However, a full constitutional discourse to legitimise the actions of the supranational institutions only came into being from the late 1970s onwards, as demonstrated in Chapter 4, when European law academia abandoned its formalist approach to European law and adopted a constitutional understanding of the European legal order. By the late 1980s, a constitutional practice was thus fully developed by the supranational institutions and European law academia and potentially laid the constitutional foundation for a move towards a federal EU during the Maastricht Treaty negotiations.

However, in contrast to the mainstream thesis on how European law developed, the member states did not readily acquiesce to the constitutional practice because they held a legislative veto right from 1966 onwards, as argued by Weiler. As Chapter 5 demonstrates, the real reason the constitutional practice was allowed to develop relatively unchecked was that the member states split over the question. This split had two consequences. On the one hand, national governments could not agree to reign in the ECJ despite the strong opposition to the constitutional interpretation of European law in several member states. France was for example ready several times to clip the wings of the court to stop the further development of a constitutional practice, but the smaller states including the Netherlands, Luxembourg, Belgium and Denmark defended the court. On the other hand, there was no consensus among national governments to codify the constitutional doctrines of the ECJ. The constitutional practice thus did not obtain the formal acceptance from the member states.Footnote ⁸² Chapter 5 thus demonstrates that the scepticism of several member states towards the constitutional practice was a long-term phenomenon stretching from the legal revolution in 1963–1964 to the negotiations of the Maastricht Treaty.

This is further confirmed by Chapters 6, 7, 8 and 9 that give a solid impression of how the constitutional practice was received at member state level. The book includes studies of four member states: France, West Germany, the Netherlands and Denmark. The four case studies are to some extent representative of the broader circle of member states that went from six original states: France, West Germany, Italy, the Netherlands, Belgium and Luxembourg to nine with the first enlargement in 1973, adding Britain, Denmark and Ireland, and finally to twelve when Greece (1981) and Spain and Portugal (1987) also joined. We include the two most important large states, France and West Germany, the most important country from the Benelux group, the Netherlands, and one of the newcomers from the first enlargement, Denmark. At the same time, this book only constitutes a first attempt to the write the general history of how member states received European law.Footnote ⁸³ Member states such as Italy, Belgian, Britain and Spain all play major roles in how European law developed and we urgently need more historical research at member state level.Footnote ⁸⁴

As the battle over the constitutional practice of European law played out at the European level, the member state institutions, ranging from governments and administrations to national courts and societal actors, all reacted in diverse ways to the development of the European legal order in the 1960s and 1970s. This was partly because the impact of European law only began to be seriously felt in the member states from the late 1970s onwards. Whereas national governments split in the Council of Ministers over the virtues of the constitutional interpretation of the ECJ from the late 1960s onwards, the reactions of national administrations and courts in most member states were generally sceptical of what was considered an unwarranted encroachment on member state prerogatives. National administrations in the member states typically attempted, very often successfully, to contain the impact of ECJ judgments and doctrines in order to mediate the consequences of European legislation to avoid interference in domestic politics. This pattern also includes otherwise pro-European member states such as the Netherlands and West Germany. Courts of the member states reacted in more complex configurations.

A general trend was that most national courts ignored European law either because of a lack of basic knowledge or because they considered it just another kind of international law that was best handled by the executive or legislative power. Across the member states national courts thus remained sceptical vis-à-vis the constitutional practice of the ECJ. The most important exceptions to this trend came from Belgium and the Netherlands (Chapter 8) where national courts relatively quickly began to cooperate with the ECJ and generally supported its constitutional case law. In West Germany (Chapter 6) and Italy, courts were also quick to engage, however, here the respective Constitutional Courts played a major role in launching a highly critical dialogue with the ECJ over the status of basic rights in European law and did not fully accept the constitutional interpretation of the ECJ. With the general passive approach of national courts to engage with European law, the Euro-lawyers explored by PavoneFootnote ⁸⁵ thus played a significant role in the 1960s and 1970s producing the cases on basis of which the ECJ could further develop and refine its constitutional doctrines, as also demonstrated by Chapter 7. The book finally demonstrates that the rapid development of the European legal order by the ECJ in the 1970s often caused controversy in the member states and led to several important attacks by national courts on the ECJ, most famously the Solange judgment by the West German Constitutional Court (Bundesverfassungsgericht, BVerfG) in 1974 and the Cohn Bendit judgment by the French Council of State (Conseil d’État) in 1979. Here Chapters 6 and 7 provide new rich stories of these key rebellions against the constitutional practice in Germany and France. All in all, member state receptions were more reluctant and sceptical than hitherto understood by the state of the art. However, at the same time the process was co-constitutive. National courts through their interaction with the ECJ, even if at time negative, contributed indirectly to the building of the European legal order. The varied national responses to the constitutional practice meant that the European legal order eventually became a patchwork, whose parameters continue to be part of the European judicial dialogue to this very day.Footnote ⁸⁶

Finally, the book argues that a complex and awkward stalemate developed in European law in the 1980s and early 1990s. On the one hand, the member states had to come to terms with the necessity of cooperating more loyally with the ECJ in the existing European legal order because from 1986 onwards the latter would become the legal basis of the Single Market. The analysis of the member states in Chapters 5, 6, 7, 8 and 9 offer unmistakable evidence of this shift in the priorities of the member states. The political and economic dynamics of the Single Market Project meant that it quickly became a central part of the European policies of all the member states. Consequently, there was now no way that national courts and administrations could continue to ignore the key features of the European legal order, including participation in the system of preliminary references, the doctrine of primacy and accepting the judgments of the Luxembourg court. Denmark for example, as demonstrated in Chapter 9, had to give up its strategy of ignoring or containing European law administratively in the late 1980s when two spectacular cases on respectively the ‘Buy Danish clause’ in the building of the bridge over the Great Belt and the AMBI labour market contribution of Danish employees blew up in the faces of Danish policy makers. Denmark was by no means alone in realising that European law could now not easily be ignored. This acceptance by the member states to contribute loyally to the functioning in the legal order built by the ECJ was expressed in the reference to the acquis communautaire in the Maastricht Treaty.Footnote ⁸⁷ The member states thus finally accepted to base the new European Union on the concept of the acquis developed by the Commission.

On the other hand, this shift in attitudes towards European law did not mean that the member states accepted the constitutional claim underlying the case law of the ECJ or European constitutionalism as the core legitimating principle underlying the new European Union.Footnote ⁸⁸ It was true that new legal reality prompted important new decision by three Supreme or Constitutional Courts from the largest member states, the Italian Constitutional Court (Corte Costituzionale) (1989), the Conseil d’État (1989) and the BVerfG (1993) that underlined their de facto acceptance of the way the European legal order functioned, including the need to participate in the preliminary reference system and respect the doctrine of primacy. However, the same decisions also rejected the constitutional interpretation of European law promoted by the ECJ. Instead, the three supreme courts defined the nature of European law from their own national vantage point. The EC/EU only existed, they argued, because the member states had delegated precisely defined competences to common institutions at European level. This implied that European law did not have constitutional autonomy and legitimacy, as claimed by the ECJ.Footnote ⁸⁹ The rejection of European constitutionalism by the supreme courts of three of the most important member states was mirrored in the negotiations of the Maastricht Treaty in 1990–1991. Here the majority of national governments decided to place the European Council as the central institution in the new Union. National governments had since the establishment of the European Council in 1974 used the institution to dominate the political agenda of the EC. Collectively, national executives had thus strengthened their grip over the development of the EC. The new EU further consolidated and formalised the dominance of the intergovernmental pillar in the process of European integration. A majority of national governments rejected the plans of the Jacques Delors Commission to base the new European Union on a single (constitutional) treaty as a first step towards a federal Europe.Footnote ⁹⁰ Instead, the Maastricht Treaty was organised in three pillars, two of which were based on intergovernmental principles of cooperation. The pillars have since been dissolved since the Lisbon Treaty (2008), however, the tendency of the European Council to occasionally opt for intergovernmental solutions continues. European constitutionalism was thus not adopted as the legitimating principle of the new European Union and the constitutional practice that had developed in European law did not obtain the ultimate vindication from national governments.

The defeat of European constitutionalism in the early 1990s was a central event in the making of the new EU, which as a result not only became dominated by the intergovernmental pillar but also did not take the shape of a full rule of law Union. Despite this defeat the battle over the potential constitutional nature of the EU did not end in 1991. It has continued these last more than thirty years and remains a fundamental fault line in the present-day EU. Over the last three decades the CJEU, supported by the supranational institutions and European law academia, have continued to develop and promote the constitutional features of the European legal order, while the gravity of political power still remains in a European Council that is not fully bound by the European rule of law. This duality continues to create tensions and ambiguity in an ever more powerful and influential Union. This book has explained why this situation first came into being. It will now be up to a new team of historians to explore the period since 1993 and tell us why the stalemate that developed from 1986 to 1993 has still not been resolved.

We hope this book will be read not only by lawyers and historians, but also social scientists. Although the chapters are in many respects pieces of legal history, the interpretation they collectively offer of the development of European law in what we might call its formative period from 1950 to 1993, and the new empirical insights they present, are certainly an important contribution to the broader field of law and politics studies today. We finally have a new interpretation of the history of European law in this period, built on solid empirical work, which can replace the old mainstream interpretation that has informed so much legal and social science scholarship over the last forty years.

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One last remark on the structure of the book is warranted. The chapters of the book occasionally deals with the same seminal court cases or major developments in the history of the European law although analysed from different angles. We have prioritised that it should be possible for a reader to fully understand the analysis of each chapter on its own without having to read the entire book from start to finish. This means, however, that repetitions cannot be avoided and that some events will figure across several of the chapters of the book.