Detention in the context of counterterrorism and armed conflict: Continuities and new challenges

Abstract This article explores recent practices of States in relation to counterterrorism and armed conflict detention. Recent cases in the courts of the UK and US are drawn on to demonstrate the continued defence by those States of their administrative detention practices. Furthermore, the practice of other States in adopting new administrative detention laws as part of their counterterrorism strategies is explored. Finally, two examples of contemporary controversies are then considered to show where much of the debate is likely to be focused in the coming years, namely the use of other administrative measures short of detention, particularly assigned residence, and detentions carried out by armed groups that are supported by foreign States.


Introduction
In the wake of 9/11, counterterrorism and armed conflict came to be seen as inseparable, both operationally, in the sense that the US's and others' operations against al-Qaeda were part of the broader invasion and occupation of Afghanistan, and legally, in the sense that States sought to justify their counterterrorism policies on the basis that they fell within an armed conflict and were subject to international humanitarian law (IHL). This phenomenon, of course, played out particularly publicly in the context of administrative detention or internment, 1 where debates raged over the appropriate regulatory framework. Whilst some saw this in terms of a stark "criminal law versus military detention" binary, 2 others emphasized the possibility of adhering to a human rights framework whilst engaging in administrative detention. 3 Still others raised concerns with the emerging idea of entrenching permanent, formalized models of administrative counterterrorism detention. 4 The US and UK, amongst others, were particular advocates of an administrative detention regime in the context of counterterrorism. 5 Soon after 9/ 11, the UK derogated in part from Article 5 of the European Convention on Human Rights (ECHR) and adopted its infamous 2001 Anti-Terrorism, Crime and Security Act. 6 Part 4 of the 2001 Act introduced a domestic system of indefinite administrative detention for those certified as "international terrorists" by the Home Secretary, with appeal to, and six-monthly periodic reviews by, the Special Immigration Appeals Commission (in place of ordinary judicial review). In many ways, this system of administrative detention looked a great deal like that provided for under the Fourth Geneva Convention in respect of civilians The AUMF has been invoked by the US government as the basis for military operations in multiple jurisdictions. 17 Curtis Bradley and Jack Goldsmith have commented that the AUMF has been transformed "from an authorization to use force against the 9/11 perpetrators who planned an attack from Afghanistan into a protean foundation for indefinite war against an assortment of terrorist organizations in numerous countries". 18 The US Supreme Court confirmed that the "necessary and appropriate force" authorized by the AUMF provided domestic legal authority to detain, 19 with Congress largely codifying the Obama Administration's definition of the scope of this authority as covering persons who "planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001, or harbored those responsible for those attacks" as well as persons who were part of or substantially supported al-Qaeda, the Taliban, or associated forces that are engaged in hostilities against the United States or its coalition partners, including any person who has committed a belligerent act or has directly supported such hostilities in aid of such enemy forces. 20 This standard is seen as grounded in "longstanding law-of-war principles", premised on a right to detain until the relevant hostilities have ended. 21 Whereas the Supreme Court extended the right of habeas corpus under the Suspension Clause of the US Constitution to Guantanamo detainees, 22 the extent of such judicial review and the evidential and procedural standards applied by the District of Columbia (DC) Circuit Court make it very difficult for detainees effectively to challenge their detention. 23 In addition, the DC Circuit has upheld the government's refusal to extend the right of habeas review to those detained in Afghanistan ("an active theatre of war"), even if they were captured elsewhere and transferred there. 24 This post-9/11 detention practice of the US and UK was marked by a desire to limit or exclude counterterrorism and armed conflict detention from ordinary law and ordinary legal processes. The last decade has seen a general winding down of detention operations in practice by these two States in the context of transnational terrorism. However, the next two sections below will demonstrate that the general approach of isolating counterterrorism detention from ordinary legal processes has continued to be pursued by both the UK and US in their L. Hill-Cawthorne ongoing defence of their practices. The consequence has been the further entrenching of a counterterrorism detention policy that follows closely the kind of detention associated with international armed conflict, excluding normal procedural standards and typical judicial control. 25 This ongoing practice of the UK and US is not only important as a precedent for those States, should they rely again on detention as a counterterrorism tool in the future, but also as a precedent for other States, which may view these positions of the UK and US as giving legitimacy to their own practices. Indeed, the fourth section of this article will demonstrate that a number of other States do still rely on existing and newly adopted administrative detention regimes as part of their counterterrorism strategy. Together, the next three sections of the article will seek to show that, despite suggestions to the contrary, 26 States still advocate and rely on administrative detention in the context of counterterrorism that mirrors that applicable under IHL in international armed conflicts. Thus, the post-9/11 practice of relying on extraordinary wartime detention powers as an analogy for counterterrorism detention, instead of the criminal justice system, has become normalized. Alongside this continuity in practice, the last section of this article then concludes by suggesting some of the new detention-related issues in the context of counterterrorism that are likely to dominate debates in this area in the coming years.

Recent US practice on Guantanamo and the Due Process Clause
A series of recent Guantanamo cases going through the DC Circuit Court demonstrates the continued defence by the US of their IHL-inspired model of counterterrorism detention. These cases have been brought by petitioners seeking the application of the Due Process Clause of the Fifth Amendment to the US Constitution in their habeas corpus claims. The Supreme Court in Boumediene required detainees to be given a "meaningful" 27 review. This led the DC Circuit 25 And this particular practice around detention forms part of and contributes to a broader context of increasingly aggressive counterterrorism strategy: M. Nowak and A. Charbord, above note 5, p. 25 ("… enhanced interrogation, secret detention and extraordinary rendition have given way to bulk surveillance and increased use of armed drones; and the moment that governments start criminalizing preparatory acts of terrorism has moved forward in time, with recent measures that target 'extremism' in the absence of any link to violence" Detention in the context of counterterrorism and armed conflict: Continuities and new challenges to develop specific evidential and procedural principles to apply in the Guantanamo habeas litigation (though with inconsistencies and frequent disagreements between judges). 28 However, application of the Due Process Clause would bring those processes more in line with those well-established rules applicable, inter alia, to pre-trial criminal detention. 29 Importantly, the Due Process Clause is also invoked by a number of the petitioners to support their challenge of the long duration of their detention under the AUMF, which, as indefinite detention for the duration of hostilities, reflects the analogy drawn by the US to the internment regime applicable to prisoners of war under the Third Geneva Convention. 30 Three recent and ongoing cases raise this constitutional question. In the first, Qassim v. Trump, the DC Circuit Court in 2019 overturned the District Court's finding that earlier Circuit Court jurisprudence in Kiyemba v. Obama 31 categorically barred the application of the Due Process Clause to Guantanamo detainees, holding instead that the only issue before the Court in Kiyemba concerned the substantive question of whether detainees unlawfully held had a substantive right to release in the US. 32 The question over the application of the procedural rights under the Due Process Clause to the habeas hearings remained unresolved and was remanded back to the District Court. 33 The particular claim by the petitioner in Qassim was that the Due Process Clause required that he and his counsel be given access to the classified material informing the government's decision to detain, including exculpatory evidence. 34 In the second case, Al-Hela v. Trump, a different panel of the DC Circuit held in 2020 that previous Supreme Court and Circuit Court precedent did establish that the Due Process Clause, including the procedural rights therein, does not extend "to aliens without property or presence in the sovereign territory of the United States". 35 In taking this categorical approach, the Court rejected the 28 36 The petitioner's particular procedural claims in this case again concerned the withholding of evidence from himself and his counsel, as well as the reliance by the government on hearsay, which he claimed violated both the Suspension Clause and the Due Process Clause. In addition to rejecting the application of the Due Process Clause entirely, the Circuit Court held that the use of hearsay, as well as the withholding of evidence from detainees and their counsel (and the hearing of it by the court ex parte), were not, as such, incompatible with the Supreme Court's requirement of a "meaningful" habeas review. 37 Importantly, Al-Hela's substantive challenges regarding the basis and duration of his detention were also rejected by the Court. First, in accordance with previous case law, the Court confirmed that the petitioner's detention was authorized by the AUMF on the basis of a "preponderance of the evidence" standard. 38 Second, it rejected the claim that the long duration of his detention (since 2004) and the US's apparently unending war on terror meant that Justice O'Connor's prescient point in Hamdi regarding the possibility of an unravelling of the argument that the AUMF authorizes detention for the duration of the hostilities was now being realized. 39 The Circuit Court held that the AUMF imposes no time limit on the President's authority to detain enemy combatants … The government maintains that the War on Terror is an ongoing conflict involving combat operations by the United States and its allies abroad. Courts lack the authority or the competence to decide when hostilities have come to an end. "The 'termination' of hostilities is 'a political act.'" 40 The petitioner had also attempted to challenge his indefinite detention as incompatible with the substantive rights under the Due Process Clause, but this failed as a result of the Court's findings regarding the scope of the Clause. 41 In the third case, Ali v. Trump/Biden, a petition for certiorari was refused in May 2021 by the Supreme Court following the DC Circuit Court's denial of the 36 Al-Hela v Trump, ibid., p. 142. Boumediene had established "at least" three factors for determining the extra-territorial reach of the Suspension Clause: "(1) the citizenship and status of the detainee and the adequacy of the process through which that status determination was made; (2) the nature of the sites where apprehension and then detention took place; and (3) the practical obstacles inherent in resolving the prisoner's entitlement to the writ": Boumediene, above note 22, p. 766. 37 Al-Hela, above note 35, pp. 135-138. 38 Ibid., pp. 130-135. 39 Hamdi, above note 19, p. 521 ("[i]f the practical circumstances of a given conflict are entirely unlike those of the conflicts that informed the development of the law of war, that understanding [that the AUMF authorizes detention for the duration of hostilities based on 'longstanding law-of-war principles'] may unravel"). 40 Al-Hela, above note 35, p. 135 ("[s]o long as the record establishes the United States military is involved in combat against Al Qaeda, the Taliban, or associated forces, we have no warrant to second guess fundamental war and peace decisions by the political branches"). 41 Ibid., p. 140 ("[w]e need not assess whether Al Hela has articulated a cognizable due process right because longstanding precedent forecloses any argument that 'substantive' due process extends to Guantanamo Bay").
Detention in the context of counterterrorism and armed conflict: Continuities and new challenges petitioner's habeas application in 2020. 42 As in Al-Hela, the petitioner in Ali invoked both the substantive and procedural aspects of the Due Process Clause to challenge his detention. Although the Circuit Court, following Qassim and in contrast to Al-Hela, considered the District Court's categorical rejection of the application of the Due Process Clause to Guantanamo to be "misplaced" 43 given the Supreme Court's more nuanced references in Boumediene to the different elements that might feed into a "meaningful" review, 44 for the same reasons it also did not accept what it saw as the petitioner's "wholesale" application of the Due Process Clause to Guantanamo. 45 Holding that it need not resolve the constitutional question, 46 the Court assessed each of the petitioner's substantive and procedural challenges and took the view that the Due Process Clause, even if it did apply, would be of no help to him.
Of particular interest here is what the Court said about the length of Ali's detention. First, the Court held that substantive due process does not as such prohibit the very lengthy detention that he has faced, particularly in light of the Periodic Review Board's findings that he continues to pose a threat. 47 Second, the Court dismissed Ali's procedural due process claim that his extended detention meant that the government now needed to show by clear and convincing evidence that he continues to pose specific threats. 48 Ali invoked the Supreme Court's Rasul case to argue that the government should now be held by a stricter standard in light of the long duration of his detention. 49 The Court held, however, that previous case law had acknowledged the possibility of very lengthy detention under the AUMF without considering that this affected the standard to be applied in review. 50  Indeed, Ali agrees that, if the hostilities covered by the AUMF were a more traditional type of war that continued for this same length of time, there would be no substantive due process objection to continued detention … Yet, Ali cites no authority suggesting that the form of hostilities that enemy combatants undertake changes the law of war's authorization of their continued detention, especially when, as here, the government has found that the threat Ali poses continues. 51 Thus, in both Al-Hela and Ali, the Circuit Court rejected the claims that the long duration and indefinite nature of the petitioners' detention as such rendered it unconstitutional (whether under the Suspension Clause or the Due Process Clause). In Al-Hela, the Court focused on domestic constitutional considerations around separation of powers, viewing the termination of hostilities as a "political" act, to be determined unilaterally by the executive. In Ali, on the other hand, it is clear from the above quote that the Court considers such lengthy detention to be consistent with international humanitarian law, suggesting that IHL indicates no difference here based on the nature of the conflict. In its recent brief opposing Ali's petition for certiorari to the Supreme Court, the Biden Administration reiterates this argument: Neither precedent nor common sense suggests that the government's detention authority should dissipate simply because hostilities are protracted … The risk that a combatant will return to the battlefield lasts as long as active hostilities remain ongoing-and petitioner has not disputed that they remain ongoing here … An individualized determination of dangerousness has never been a prerequisite to the detention of enemy combatants. 52 Yet the position under IHL does, in fact, differ in this regard depending on the nature of the conflict. Whilst it is true that in international armed conflicts there is a presumption of internment of combatants for the duration of hostilities, 53 there is no such presumption applicable in non-international armed conflicts. 54 And this is for good reasons. As I have shown elsewhere, the principles that inform this presumption vis-à-vis members of State armed forces in international armed conflicts do not apply to non-State armed groups, such that analogies to the internment regime for combatants/prisoners of war are inappropriate. 55  someone is a member of an armed group, 57 presuming that detention of those with this "status" is necessary for the duration of hostilities is insufficiently nuanced. 58 Just as membership of an armed group will often be based on functional, as opposed to formal, criteria, so leaving that armed group also will be. 59 In the context of the US's ongoing war on terror, the need to assess the necessity of continued detention on the basis of an individualized threat determination, as opposed to presuming necessity on the basis of "status" for the duration of hostilities, is all the more pressing given the extremely vague contours of the relevant conflict and the parties thereto, a point long recognized. 60 It is this limitation that continues to be the core problem with habeas reviews of Guantanamo detainees, as it conditions the court's power to order release on the executive's determination of whether the conflict has ended. The Periodic Review Board process, though it does in theory assess whether detention continues to be necessary for security, results in only a recommendation to the Secretary of Defense, 61 with Congress in recent years heavily limiting the ability to transfer detainees out of Guantanamo. 62 These recent cases suggest that, notwithstanding the passage of nearly twenty years since the opening of the detention facility at Guantanamo Bay to house detainees captured in the US's war on terror, there remain fundamental continuities in the legal approach taken by the courts and by the government regarding detainees. First, the infamous and heavily criticized notion of a "war on terror" continues to inform the legal framework governing Guantanamo detainees and was invoked explicitly by the DC Circuit in Al-Hela. 63 Second, the presumption of indefinite administrative detention for the duration of hostilities remains the core part of the US's detention policy, even as the idea of ongoing hostilities against a defined enemy has long dissipated. Third, attempts to bring the habeas proceedings closer in evidentiary and procedural standards to more ordinary judicial proceedings through extension of the Due Process Clause continue to be rebuffed. Indeed, the Biden Administration's brief on this point in Ali opposing the petition for certiorari to the Supreme Court takes an almost identical position to the Trump Administration in earlier iterations of the case. 64 This is not to suggest that there has been no progress. On the contrary, the Supreme Court ensured at least some process for Guantanamo detainees in the first decade, and the vast majority of detainees have now been transferred out of Guantanamo. 65 In addition, there has been some push to bring those captured in more recent years as part of the US's war on terror before ordinary criminal courts. 66 Yet the continued refusal to bring Guantanamo detainees within a more ordinary legal framework, and the continued use of inappropriate analogies to the IHL internment regime applicable to combatants in international armed conflicts, shows the extent to which this precedent is now firmly entrenched in US counterterrorism policy. In addition, whilst the US's own counterterrorism detention practices have wound down, this precedent risks serving a legitimizing function for similar practices that continue in other States, as will be seen later in the article.

Recent UK practice in litigation concerning overseas detention operations
In UK practice too we can see core continuities with the past in the approach taken in recent cases, again creating certain worrying precedents for other States. Whereas much of the litigation in the US has concerned habeas petitions by Guantanamo detainees, the litigation in the UK has largely come from detainees held in Iraq and Afghanistan in the form of public law (principally Human Rights Act) and private law actions. The purpose of this section is not to review these cases, which have received significant coverage elsewhere. Instead, two points will be made. First, the UK government, like the US government in its "war on terror", has continued to argue that its detentions in the context of Iraq and Afghanistan are to be judged not against any ordinary law regime but against international humanitarian law. Second, the jurisprudence of the UK Supreme Court in this area has created a real risk that the internment regimes applicable in international armed conflicts could be applied in situations outside armed conflict (international or non-international), which stricter human rights standards should regulate.
On the first point, the UK government has sought to exclude both its domestic law on habeas corpus and its obligations under the ECHR from detainees held in Afghanistan and Iraq. With respect to habeas corpus, the UK government, like the US government, has argued that UK courts do not have Detention in the context of counterterrorism and armed conflict: Continuities and new challenges jurisdiction to hear habeas petitions from military detainees in Iraq and Afghanistan. 67 Unlike the US courts, however, which have rejected habeas petitions from those held in conflict zones, 68 the UK Supreme Court has held that there is nothing preventing the extension of habeas corpus to detainees overseas that are within the control of the UK. 69 The UK Supreme Court approaches this question differently to the US Supreme Court, asking not whether there is sufficient territorial control by the State to justify the extension of the writ, but rather whether the individual is within the (actual or potential) control of the State. 70 This is important for those detained abroad by the UK in any situation, whether or not there is an armed conflict. With respect to the ECHR, as is well known, the UK in Hassan v. UK successfully argued for the first time before the ECtHR that Article 5 of the ECHR was modified in an international armed conflict by IHL. 71 The UK then sought to extend this argument to non-international armed conflicts in its domestic litigation in relation to detention operations in Afghanistan. 72 This was rejected by the High Court and Court of Appeal. 73 A majority of the UK Supreme Court agreed with the government that the grounds and procedures (taken from the Fourth Geneva Convention) acceptable to the Strasbourg Court in Hassan for the purposes of complying with Article 5 of the ECHR in international armed conflicts would also be acceptable in the case of the noninternational armed conflict in Afghanistan. However, they did so, not on the basis of IHL, but rather relevant Security Council resolutions, which they viewed as providing a sufficient legal basis for detention. 74 The UK Ministry of Defence has subsequently amended its detention policy in light of Lord Sumption's judgement in Al-Waheed/Mohammed, in which he held on the facts that the detention review procedures in Afghanistan did not comply with Article 5(4) of the ECHR even after reading down what that provision required. 75 Thus, in 2020 the Ministry of Defence's detention policy was revised so as to create a new Detention Review Authority, which is separate from and outside the chain of command of the authority ordering detention and which has the power to order release following initial and periodic (six-monthly) reviews. 76 Though certainly helping to address some of the concerns with the previous process, the new policy states that the Detention Review Authority may consist of a single person, which is not compatible with IHL. 77 The revised policy applies to all those detained by the UK on preventive, security grounds (other than prisoners of war) in any armed conflict, whether international or non-international. However, the reasoning of Lord Sumption in Al-Waheed appears not to be limited to armed conflicts. Instead, in order to overcome the very different context of the Hassan and Al-Waheed cases (namely, that in the former the Court was able to draw on the rules under the Fourth Geneva Convention on civilian internment in international armed conflicts, which was not possible in the latter given the dearth of rules for noninternational armed conflicts), Lord Sumption appeared to read the Hassan judgement as setting out a general minimum content for Article 5 of the ECHR, for which derogation is not necessary: It is in my opinion clear that [the Grand Chamber] regarded the duty of review imposed by articles 43 and 78 of the Fourth Convention as representing a model minimum standard of review required to prevent the detention from being treated as arbitrary. They were adopting that standard not just for cases to which those articles directly applied, but generally. 78 This is a long way from the Grand Chamber's clear statement that: [i]t can only be in cases of international armed conflict, where the taking of prisoners of war and the detention of civilians who pose a threat to security are accepted features of international humanitarian law, that Article 5 could be interpreted as permitting the exercise of such broad powers. 79 Lord Sumption's approach creates a real risk that the limited procedural protections for civilian internees under the Fourth Geneva Convention will be viewed as the generally applicable standards that are sufficient to meet Article 5(4) of the ECHR in any circumstance, including outside armed conflict. The analogy to the approach of the US government and federal courts in interpreting the US's detention authority under the AUMF by reference to what is permitted under the law of international armed conflict is clear. I have argued elsewhere that the philosophy of IHL, with its presumption of necessity, should make us very cautious about any attempt to extend it (whether in respect of non-international armed conflicts or situations outside armed conflicts altogether) in a way that might be seen as automatically modifying international human rights law. 80 The preference should instead be to require States to derogate from the latter and thereby demonstrate an actual necessity to depart from ordinarily applicable legal standards. Once again, this risks creating a precedent that may influence other States in extending the 77 On the need for a review body to consist of more than one person in the context of civilian internment review under the Fourth Geneva Convention, see L. Hill-Cawthorne, above note 7, p. 53. 78 Al-Waheed, above note 15, para. 66 (Lord Sumption). 79

Recent examples of administrative detention laws
Whereas the US and UK have wound down their post-9/11 detention operations in recent years, administrative detention remains a key part of many other States' counterterrorism tools. In particular, in the context of counterterrorism, we have recently seen a number of States adopt new domestic laws permitting administrative detention, other States applying or expanding existing domestic laws permitting administrative detention, and others relying on extended forms of pre-trial detention in terrorism cases that in practice are sometimes indistinguishable from administrative detention. This section briefly explores examples of each in order to demonstrate the continuing reliance of many States on administrative detention regimes in counterterrorism. Together with the previous sections, which showed the continued defence of administrative detention for counterterrorism purposes by the US and UK, these examples confirm that such forms of detention remain a prominent part of counterterrorism policy around the world.
As an example of a State recently adopting a new domestic statute permitting administrative detention, we can look to Malaysia, which has a long history of domestic preventive detention laws. 81 In particular, its controversial Internal Security Act 1960 (ISA) provided for indefinite administrative detention and remained in force until its repeal in 2012. However, shortly after the repeal of the ISA, Malaysia adopted its new Prevention of Terrorism Act in 2015 (POTA), 82 which reintroduced the power of (effectively indefinite) administrative detention outside the criminal justice system, 83 and which in some respects is more draconian than that under the ISA. 84

L. Hill-Cawthorne
appointed by the King. 86 The POTB may make a detention order of up to two years where it is satisfied that the individual "has been or is engaged in the commission or support of terrorist acts involving listed terrorist organizations in a foreign country or any part of a foreign country" and where "it is satisfied that it is necessary in the interest of the security of Malaysia". 87 Detention orders can then be extended by the POTB for further periods of up to two years at a time with no limit on the number of renewals. 88 There are no stipulated procedures or due process standards governing the POTB's decision-making and no right of access to a lawyer. The detainee can make representations to an Advisory Board, provided for under the Malaysian Constitution, but members are again appointed by the King and its recommendations are not binding. 89 The 2015 Act also contains an ouster clause excluding the jurisdiction of any court to review on the decisions of the POTB. 90 The POTA, as well as other domestic laws providing for extended detention in terrorism cases, continue to be relied upon by the government, and in August 2020 it was reported that 1032 individuals were detained without trial in Malaysia under national security laws. 91 Human rights non-governmental organizations have been highly critical of Malaysia's counterterrorism statutes, given the stark departure from ordinarily-applicable human rights standards on the right to liberty and judicial review of detention. 92 The POTA reflects an administrative detention regime in the strictest of senses, permitting indefinite detention on the basis of security threat, outside the criminal justice system, ordered and fully overseen by the executive with no recourse to substantive judicial review. It is very similar to the internment regime provided under the Fourth Geneva Convention for international armed conflicts, though the lack of independent review capable of ordering release means it would not comply even with that regime were it applicable. 93 Sri Lanka is an example of a State that continues to rely upon (and has extended) long-established domestic administrative detentions laws as part of its ongoing counterterrorism strategy. The Prevention of Terrorism Act of 1979 (PTA), adopted in the context of the government's conflict with separatist insurgencies including the Liberation Tigers of Tamil  The same administrative detention regime applicable during Sri Lanka's long civil war thus continues to be applied as part of its post-conflict counterterrorism policy. Moreover, notwithstanding assurances from the government, including to the European Union and United Nations (UN) Human Rights Committee, that it would repeal the PTA, 96 in March and April 2021, respectively, the Sri Lankan government adopted two sets of Regulations under the PTA expanding extraordinary powers of detention. 97 Whilst the second regulation proscribes eleven Islamist organizations, with extended criminal penalties for individuals associated with them, 98 under the first, any person "who causes or intends to cause commission of acts of violence or religious, racial or communal disharmony" may be referred by a Magistrate to a "rehabilitation programme" in a "reintegration centre" for up to two years, with the power of release resting with the Minister of Defence. 99 The International Commission of Jurists has criticized these regulations as likely being used to (further) target minority religious and ethnic communities with administrative detention. 100 In June 2021, the European Parliament adopted a resolution condemning Sri Lanka's continued reliance on the PTA and its adoption of these new regulations L. Hill-Cawthorne as incompatible with the right to liberty and the due process guarantees in Article 9 of the International Covenant on Civil and Political Rights (ICCPR). 101 Israel also continues to rely on established administrative detention laws as part of its counterterrorism strategy. Separate, though similar, laws exist for Israel and the Occupied Palestinian Territories (OPT). In respect of the OPT, a military order grants commanders the power to order detention initially for up to six months (renewable indefinitely) where they reasonably believe such detention to be necessary "for reasons to do with regional security or public security". 102 In respect of Israel, the Emergency Powers (Detention) Law of 1979 similarly permits the Minister of Defence to order detention for up to six months (again renewable indefinitely) where they reasonably believe such detention to be necessary for "reasons of state security or public security". 103 Under the 2002 Incarceration of Unlawful Combatants Law, which has been used as the basis for administratively detaining residents of Gaza, the Chief of the General Staff of the Israel Defence Forces may order the detention of a person where they reasonably believe them to be an "unlawful combatant" whose detention is necessary for State security. 104 The law creates a rebuttable presumption that a person who is a member of or participated in acts of a group engaging in hostile acts against Israel is someone whose release would harm State security so long as hostilities with that group are ongoing. 105 Moreover, the Minister of Defence is given the power to identify groups engaging in "hostile acts" against Israel for these purposes. 106 There is a clear analogy here to the shortcomings in the Guantanamo habeas reviews, discussed above, which treat as dispositive the government's position that hostilities are ongoing in its "war on terror". Unlike in the case of Malaysia and Sri Lanka, under each of these administrative detention regimes, though with some differences, initial and periodic review is by a court as opposed to administrative body. 107 Nevertheless, these judicial reviews have been criticized as showing deference to the military and applying draconian procedures. 108 Israel continues to rely on these various administrative detention laws as a tool in counterterrorism, 109 and its "serial derogation" from Article 9 of the ICCPR (introduced on ratification in 1991) remains in effect. 110 Administrative detention by Palestinian authorities on the basis of vague laws also continues to be emphasized as cause for concern by monitoring bodies. 111 Furthermore, in addition to its existing administrative detention laws, Israel recently consolidated and expanded its counterterrorism legislation in a 2016 statute that, inter alia, creates harsher sentences for those convicted of terrorism-related offences and normalizes the powers of the government previously exercised under longstanding emergency legislation to designate groups as terrorist organizations. 112 France historically has adopted a very different approach to counterterrorism detention than Israel and the other States discussed above, relying principally on ordinary criminal law. 113 However, over the last decade especially, it has adopted a number of specialized laws that enhance counterterrorism powers and, to an extent, represent a shift towards preventive, administrative measures (albeit stopping short of administrative detention). 114 In response to the 2015 Paris attacks, the government declared a state of emergency that lasted for two years, during which it formally derogated from the ICCPR and ECHR, including Articles 9 and 5, respectively. 115 Following the 2016 Bastille Day attack in Nice, France adopted a broad new counterterrorism law that, inter alia, expanded police powers and extended the right of house arrest from one month to three; a proposal to introduce preventive detention of terrorism suspects without judicial oversight was, however, rejected. 116 This law, and a second adopted in 2017, made permanent a number of the emergency powers, including enhanced police powers and powers of assigned residence, introduced following the 2015 Paris attacks. 117 Moreover, the long-standing concept of détention provisoire continues to be relied upon, whereby persons under investigation for serious crimes, including terrorism-related offences, can be detained initially for up to one year (with the possibility of extension up to a total of four years for the most serious crimes), on the order of a juge des libertés et de la détention. 118 This system of pre-trial detention has been criticized on many grounds. 119 It has been observed that the 2015 Paris attacks contributed to an increased reliance on lengthier pre-trial detention, including for suspected foreign terrorist fighters, for whom detention pending investigation is now the norm. 120 It is important to note in this context that France has one of the highest populations of pre-trial detainees in Europe, 121 as well as one of the highest populations of detainees held for terrorism-related offences. 122 Criticisms against other States have also been made for the use of lengthy pre-trial detention in terrorism-and security-related cases. 123 The above examples of Malaysia, Sri Lanka and Israel demonstrate the continued reliance on administrative detention regimes in the context of counterterrorism. Like the post-9/11 detention practices of the UK and US, which were shown in earlier sections to still be defended by those States, these regimes are very similar to the extraordinary internment regimes applicable in international armed conflicts under IHL. Importantly, the adoption and use of these administrative detention powers are in a context where States are expanding their counterterrorism powers more generally, including through their criminal law, as demonstrated by the recent legislation in Sri Lanka, Israel and France. It has been remarked that there has also been a recent trend of extended derogations from the ECHR in the context of emergency measures that include intrusions into liberty (in the form of both lengthy pre-charge detention and house arrest) and reduced judicial oversight. 124

Going forward
The previous sections have shown that administrative detention remains a key part of many States' counterterrorism policies, and that even the UK and US, which have wound down their post-9/11 detention practices, continue to defend administrative detention regimes that sit outside the ordinary legal framework. This aspect of the contemporary practice reflects a fundamental continuity over the past two decades in counterterrorism policy. However, there are other aspects of contemporary detention-related practices in the context of counterterrorism that, though not novel, raise new challenges. It is here that much of the debate will no doubt be located over the next few years. It is on two such examples of recent practices that this section focuses. First, the growing phenomenon of other administrative, liberty-restricting measures will be explored, in particular house arrest or "assigned residence". Second, the legal controversies posed by detentions by non-State armed groups supported by States will be considered.

Assigned residence
The use of administrative measures short of detention that make an impact on the right to liberty and freedom of movement has become especially prominent in light of the recent phenomenon of foreign terrorist fighters. 125 Thus, a recent feature of counterterrorism laws across Europe is the inclusion of administrative measures, often termed "control orders", that restrict a person's movement to different degrees, measures that have long been in use in the UK. 126 This trend has been noted with concern given the tendency for such measures to apply at increasingly pre-emptive points in time and to fall outside ordinary criminal justice processes and safeguards. 127 Of particular interest here is the use of assigned residence as an administrative measure in the context of counterterrorism, given the very fine line between this measure and detention in the strict sense. Indeed, assigned residence, like administrative detention, is provided for under IHL in international armed conflicts for civilians that pose a security threat, and it is viewed and regulated by IHL as equivalent to internment. 128 It is therefore especially noteworthy that, alongside the continuing reliance on administrative detention by certain States, assigned residence is also growing in prominence in counterterrorism practices. In September 2020, for example, Switzerland adopted its new Federal Law on Police Measures to Combat Terrorism, 129 which was approved by a national referendum in June 2021. 130 Amongst the new administrative measures provided for under the law is assigned residence where an existing control order (e.g. one imposing a curfew or banning contact with specific individuals) is breached and where "there are concrete and current indications" that the person poses "a considerable threat to the life or bodily integrity of third parties" which cannot be prevented by other means. 131 Assigned residence can be ordered initially for three months and can be renewed for two further periods of three months each. 132 Whilst this should normally be in the home of the individual concerned, exceptionally they can be assigned to a different location or institution. 133 Authorization for initial assigned residence orders and their renewal is by a court (the Tribunal cantonal des mesures de contrainte in Bern). 134 The law makes it possible to obtain certain exemptions from assigned residence, and it permits limiting of contact with the outside world only to the extent necessary. 135 However, it is possible for "assigned residence" under the new law to look identical to administrative detention in a detention facility.
Indeed, the provision for assigned residence has been heavily criticized as being incompatible with Articles 5 and 6 of the ECHR. 136 Other States too have recently adopted new counterterrorism statutes that provide for assigned residence (albeit to different degrees). In France, for example, where the return of foreign terrorist fighters is equally a concern, 137 the 2017 Law on Strengthening Internal Security and the Fight Against Terrorism (SILT) introduced a number of administrative control measures into French law following the end of the state of emergency. 138 This includes a power of the Minister of the Interior to order anyone whose behaviour is considered to pose a serious security threat, and who is in regular contact with those supporting or participating in terrorism, not to go beyond the perimeters of a specified geographical area, which cannot be smaller than their town or city. 139 Any such order is initially for up to three months, renewable up to a total of twelve months. Though less restrictive of liberty than the new assigned residence orders under Swiss law, these orders under SILT have been criticized on the basis of the vague language regarding to whom they apply and the barriers to effectively challenging such orders before the Conseil d'État. 140 Other States continue to rely on existing assigned residence powers as a counterterrorism tool. This is the case, for example, with Tunisia in its ongoing state of emergency that was declared following the November 2015 attack (claimed by Islamic State) on the Presidential Guard in Tunis. Those placed in assigned residence (which in some cases appears in practice to be house arrest) include returning foreign terrorist fighters and members of domestic terrorist groups. 141 These laws and practices regarding assigned residence share the same idea as that underpinning the use of administrative detention, i.e. that special laws restricting liberty and freedom of movement, sitting outside ordinary legal processes and instead mirroring similar measures available under IHL, are necessary counterterrorism tools. The recent laws in Switzerland and France provide another example of such extraordinary powers being incorporated into permanent domestic legislation. Assigned residence, and other administrative measures short of traditional detention, will probably continue to play a prominent role in the future, and their compatibility particularly with human rights law will be an ongoing controversy.

Detainees held by armed groups
A second significant issue now confronting many States involved in overseas counterterrorism operations and armed conflict concerns the disposition of detainees held by partner armed groups. This question has, of course, arisen particularly in the context of detainees held by the Syrian Democratic Forces (SDF) in the North East, which have received support from and worked with many of the States in the Global Coalition to Defeat ISIS. 142 Particularly since the fall of Baghouz in March 2019, the SDF has detained tens of thousands of suspected Islamic State fighters and their families, with the total figure in March 2021 standing at over 63,000. 143 The question of how now to deal with these detainees has arisen, particularly in light of the reluctance of many States to accept the repatriation of their nationals that are being held by the SDF, creating a real risk of indefinite administrative detention or flawed trials by Syrian Democratic Council and Iraqi courts. 144 In addition to questions concerning the legality of detentions by armed groups and the legitimacy of refusals by national States to accept the return of foreign terrorist fighters, 145 the context of support for and partnering with armed groups by States raises legal questions regarding the responsibility of such States for those detentions (including treatment of detainees) by armed groups. Rules from multiple sources of international law create obligations on States in relation to the conduct of others. 146 Under international humanitarian law, a widely shared reading of Article 1 common to the four Geneva Conventions places obligations on all States not to aid or assist in violations of IHL by others and to do all that they can to bring such violations to an end. 147 Under the law on State responsibility, States must not knowingly aid or assist other States in the commission of internationally wrongful acts, 148 and some have argued in favour of extending this rule to include assistance to non-State actors. 149 In addition, where there is a serious breach of a peremptory norm of international law, 150 States must do all that they can to bring that violation to an end. 151 Also, under international human rights law, States' positive obligations require that they protect individuals within their jurisdiction from rights violations by non-State actors, 152 with some treaty bodies taking a very expansive approach as to when an individual falls within a State's jurisdiction. 153 In light of this background normative context, States cannot expect to outsource parts of their overseas counterterrorism operations with impunity to non-State groups operating in the region. 154 Where those non-State groups engage in detention, the States supporting them may well be in a strong position to promote compliance with international law, which is particularly important for those rules above that contain due diligence obligations. Indeed, it has been reported that a number of States involved in the Coalition have a presence of some kind in the detention camps run by the SDF. 155 In addition to the risks of indefinite detention without due process for detainees held by the SDF, there is also clear evidence of very poor conditions of detention, abuse of detainees, and disappearances. 156 This is no doubt, in part, a consequence of the total lack of planning for detention operations; given the need to avoid such humanitarian crises and given that the international responsibility of supporting States could be engaged by such breaches committed by their non-State partners, advance planning is essential. 157 In light of the increasingly prominent role once again of foreign State support for armed groups in conflicts around the world, as seen across the Middle East, Africa and Ukraine, these same issues are likely to continue to arise in future conflicts and overseas counterterrorism operations. 158

Concluding remarks
This article has demonstrated the continued prominence of administrative detention as a counterterrorism tool. In the years following 9/11, administrative detention constituted a key part of the "war paradigm" that informed many States' counterterrorism practices. For some, this has continued, and for the US and UK, which in recent years have moved away from counterterrorism detention, the IHL-inspired model of administrative detention, sitting outside ordinary legal processes, continues to be defended and constitutes a precedent for other States. However, the continued conflation between IHL and counterterrorism does not stop there. As the previous section showed, many States have recently relied upon and even expanded their administrative measures short of detention for counterterrorism purposes, including assigned residence, a measure provided for under IHL as equivalent to administrative detention. These other administrative measures, along with the controversies arising from detentions by armed groups (often with the support of States) will probably dominate much of the work in this area in the coming years.
To end, two final points are worth emphasizing. First, as has been shown above, the recent practice explored in this article sits in a context of new domestic statutes that render permanent many powers, including those having an impact on the right to liberty, previously exercised under emergency counterterrorism legislation. 159 This facilitates the gradual incursion of extraordinary powers, such as those provided for under IHL of administrative detention and assigned residence, into everyday counterterrorism practices. Second, we should remember that this relationship between IHL and counterterrorism runs in both directions. Whereas the focus here has been on the use of IHL powers in counterterrorism, post-9/11 counterterrorism practices also served as testing grounds for readings of IHL (and international human rights law) that create even more freedom for States, putting pressure on these legal regimes and their capacity effectively to regulate future conflicts. 160