As a lawyer who has represented Guantánamo detainees since the inception of the prison 20 years ago, I sometimes get asked, “What about these cases could you possibly still be litigating in 2022?” As it turns out, the answer is: quite a lot, from arcane questions about the scope of the government’s (possibly diminishing) detention authority to in-the-weeds rules governing what evidence the courts can consider against detainees. These unresolved legal issues have profound implications for our forever prison and the 39 men still detained there.

By way of background, a brief history: the first two years of litigation focused on winning access to our clients, who were being held incommunicado. The Supreme Court’s landmark Rasul v. Bush decision in 2004 held that detainees at Guantánamo could petition for the writ of habeas corpus. Despite continuing access problems, the “legal black hole” the Bush administration had attempted to create was no longer. Congress very quickly set about attempting to reverse Rasul by amending the habeas statute,  and by and large questions about the limits and duration of detention power and the sort of evidence the government would be permitted to rely on were not considered in detail by the courts until after another watershed Supreme Court decision, Boumediene v. Bush in 2008, which held that the detainees had a constitutional right to have the legality of their detentions reviewed by a court.

Starting in 2009, the district courts and the then-new Obama administration subsequently made efforts to address these questions, but, as recounted by myself and many others, by 2011 the then-sharply conservative D.C. Circuit had rendered it more or less impossible for detainees to prevail on their habeas petitions. With a handful of exceptions, the litigation ground to a halt. After a swift start transferring detainees at the outset of Barack Obama’s presidency, his administration decided not to spend much political capital seeing through his promise to close the prison, and Congress intervened unhelpfully to place hurdles in the way of certain transfers abroad. The middle years of Obama’s administration witnessed the slowest pace of releases since the prison opened, but a wave of repatriations and third-country resettlements took place in the last year of his administration.

Only 41 men remained at Guantánamo when Donald Trump took office, and all but one were still detained four years later. In the eight years since the bulk of the D.C. Circuit’s major Guantánamo decisions, the composition of the court changed — the Democrats having invoked the nuclear option to confirm three of Obama’s picks to the Circuit — and, of course, the Supreme Court became markedly more conservative.

The Scope of the Government’s Detention Power: Who Can Be Detained?

Much of the academic literature on Guantánamo since Rasul has centered on the question of who might lawfully be detained under the September 2001 Authorization for Use of Military Force (AUMF) against nations, groups, or individuals who “planned, authorized, committed, or aided” the 9/11 attacks (or harbored those persons). The courts have generally assumed, based on the understanding articulated in Hamdi v. Rumsfeld, that force authorizations import international law of war principles for the pendency of the active hostilities at issue and imply a power to detain people in the categories covered by the AUMF. The legal debate has therefore centered on the scope of that detention authority.

Habeas counsel, following traditional law-of-war precepts, generally argue that, in the non-international armed conflict against al-Qaeda and the Taliban, “membership” is so amorphous that it cannot be dispositive of the government’s detention authority; rather, some degree of active “direct participation in hostilities” is necessary to render detention lawful. The government’s position is that “membership” in a group covered by the AUMF’s broad remit is sufficient, even absent an individual’s direct participation in hostilities, to justify his detention, claiming “authority to detain persons who were part of, or substantially supported, Taliban or al-Qaida forces or associated forces that are engaged in hostilities against the United States or its coalition partners.” In a 2009 memo, the government agreed that interpretations of the detention authority conferred by the AUMF must be informed by international law. It also conceded that the boundaries of “substantial” support and “associated” forces were not sharply defined, and that “the contours of [these two] bases of detention [would] need to be further developed in their application to concrete facts in individual cases.”

The district courts initially tried to clarify the principles. In 2009, the district court in Gherebi v. Obama required that detainees have a defined role within the command structure of a group to be detainable as “part of” or “supporting” that group, and the court in Hamlily v. Obama held that mere support for a group targeted by the AUMF was not enough to support detention if the individual was not “part of” a cobelligerent organization (though support might be weighed as evidence of membership). But within the next year, several panels of the D.C. Circuit had expressed disdain for formal bright-line rules (see, for example, Bensayah v. Obama), often permitting “membership” in hostile forces to be defined in terms broad enough to approach guilt by association, as in Al-Bihani v. Obama.

In practice, the legal disputes about the quality of evidence that habeas judges can properly admit and consider (discussed in the next section) had – and continue to have – far greater practical importance than these “law of war” questions. But there is still significant litigation afoot over the question of what it means to be detainable as “part of” a group that is an “associated force” of the Taliban or Al Qaeda.

The most notable such challenge involves an Afghan national, Asadullah Haroon Gul, who is cleared for release but whom the government nevertheless argued remains detainable because of his past membership in Hezb-e-Islami Gulbuddin (HIG), which had been allied with al-Qaeda and the Taliban. In an opinion issued on Oct. 19, 2021, Judge Amit Mehta granted the writ of habeas corpus, holding that, because HIG had concluded a peace treaty with the Afghan government in 2016, ending its role as an “associated force” in the conflict, Gul was no longer lawfully detainable. Judge Mehta rejected the government’s argument that, independent of Gul’s relationship through HIG, his acts were sufficient to render him “part of” or providing “substantial support” to al-Qaeda, finding the government’s reasoning inconsistent with the structure of Congress’ pronouncements on detention authority and the law of war. To justify Gul’s detention after HIG made peace, Judge Mehta held, the government would have to show Gul’s own actions “exceeded the scope of HIG’s cobelligerency” with al-Qaeda. Because it failed to do so, the end of HIG’s co-belligerency with the al-Qaeda-Taliban axis put an end to the government’s ability to detain him. The government did not appeal the decision.

Variants of these arguments had been made before, but they did not gain traction with the district courts prior to Gul (perhaps because the D.C. Circuit had so frequently expressed a preference for a less formal, holistic analysis in rejecting individual petitioners’ similar claims). A number of detainees who remain at Guantánamo today were claimed to be detainable by dint of their membership in associated forces that no longer exist, or because they allegedly provided support to members of al-Qaeda as part of their roles within groups that were supposedly co-belligerents. The government has always argued that such individuals may also properly be deemed part of al-Qaida itself. If other district judges are willing to reject that argument, factual issues around the existence (or non-existence) of co-belligerency will assume more importance going forward.

Indeed, the question initially presented by habeas counsel – whether status as “part of” some militant group alone can justify detention, absent direct participation in hostilities – could remain relevant to the habeas cases. Seven years ago, the Supreme Court denied cert in a Guantánamo appeal, Hussain v. Obama, and Justice Breyer noted in a statement accompanying the denial that the Supreme Court

has not [yet] directly addressed whether the AUMF authorizes, and the Constitution permits, detention on the basis that an individual was part of al Qaeda, or part of the Taliban, but was not ‘engaged in an armed conflict against the United States’ in Afghanistan prior to his capture. Nor have we considered whether, assuming detention on these bases is permissible, either the AUMF or the Constitution limits the duration of detention.

Hussain did not raise the issues in his Questions Presented, and the Supreme Court still has not answered them. But the Circuit seems generally more willing to write on a blank slate now than it was in 2014, even if the Supreme Court may now be less inclined to take up these questions.

Evidentiary Rules: What Aspects of Procedural Due Process Apply?

Whether the Due Process Clause of the Constitution applies in any respect to detentions at Guantánamo is an unanswered question that has hung over the litigation since its earliest days  – it was likewise unresolved when Haitian political asylees were being detained in camps at Guantánamo in the early 1990s. After Rasul, the question was the subject of divergent opinions in the district courts. Boumediene’s functional approach to extraterritorial application of the Constitution at Guantánamo signaled that the Due Process Clause should apply. But by the time the first post-Boumediene district court decisions went up on appeal, the parties generally presumed all application of the Due Process Clause foreclosed by a single throwaway line in the D.C. Circuit’s 2009 decision in Kiyemba v. Obama.

Kiyemba was ostensibly about whether federal courts could order Uighur detainees released into the United States if they had no other safe country to go to, despite Congress having banned the transfer of any former Guantánamo detainee into the United States. The court held that the political branches’ control over immigration was absolute, trumping whatever rights the Uighur detainees might have, but noted that “the due process clause does not apply to aliens without property or presence in the sovereign territory of the United States.” Technically, the statement was dictum, and it did not follow the Supreme Court’s approach in Boumediene, but it was repeated in dictum in several other opinions of the Circuit, and a number of district judges read it as indicative of the Circuit’s view on the matter. As a result, when the procedural ground rules for adjudicating these cases were decided by the Circuit (primarily in a series of cases from 2009 to 2011, as summarized at footnote 9 of this brief), petitioners never squarely asserted that the Due Process Clause should apply directly at Guantánamo.

In the last three years, one panel of the D.C. Circuit decided that Kiyebma established no such categorical rule against application of the Due Process Clause; another held that Kiyemba’s dictum should be transformed into holding; and the D.C. Circuit, after prior hints that the question was of importance, took up en banc review of the question, with eleven judges hearing argument on Sep. 30, 2021. Decision in that case, Al Hela v. Biden, D.C. Cir. No. 19-5079, remains pending.

Without the protections of the Due Process Clause, the procedural and evidentiary rules in these cases weigh heavily in favor of the government, in a way that would be impermissible in other civilian proceedings. That has made it nearly impossible for Guantánamo detainees to win a habeas case against the government. As Senator Dick Durbin recently put it,

For nearly two decades, our nation has failed to provide due process to detainees held at Guantánamo, resulting in the use of unreliable hearsay and coerced or torture-derived evidence and a shamefully low burden of proof for depriving men of their liberty. These inadequate standards and procedures have made it nearly impossible for detainees to prevail in litigation challenging their detention.

One common example in Guantánamo cases involves the rules governing the admission of hearsay evidence. (Hearsay is generally any secondhand report of what a witness said—for instance, a document reporting what a detainee said under interrogation.). The vast majority of evidence introduced against detainees consists of hearsay interrogation records (usually of other detainees) and declarations; many of the interrogation records are anonymously sourced. The Due Process Clause bars unreliable hearsay and, if applied to Guantánamo proceedings, would require that detainees be permitted to confront the evidence against them where feasible. The first set of procedural rules set forth by the district court in 2008 to govern Guantánamo cases was consistent with due process principles: it required the government to make a motion establishing the reliability of its hearsay submissions and demonstrating the burden of producing equivalent non-hearsay evidence. For instance, before introducing a detainee’s interrogation record as evidence in another detainee’s habeas case, the government would have to show that that first detainee’s interrogation was non-coercive and would have to explain why the witness-detainee himself could not testify, subject to cross-examination. The Circuit subsequently absolved the government of these burdens in a number of decisions, but if procedural due process applies, it would support the original rule  –  making it much harder for the government to rely on the questionable “evidence” that it has built most of its cases upon.

At issue in Al Hela is hearsay evidence that (1) does not indicate who the original source of the information is, (2) is not viewable by the detainee because the government maintains it is classified, and/or (3) has been presented to the court ex parte, meaning that even Al Hela’s security-cleared counsel couldn’t see it, let alone Al Hela himself. All three problems are ubiquitous across Guantánamo habeas cases, and the threshold for the admission of such evidence would almost certainly be much higher – likely excluding much of this evidence – if the Due Process Clause applied. A number of other procedural rules –  the preponderance standard of proof, the “presumption of regularity” afforded the government’s records, and several others –  might likewise not survive scrutiny under the Due Process Clause.

It’s unlikely the Circuit decided to rehear Al Hela en banc simply in order to adopt the panel’s broad rule prohibiting any due process claims whatsoever. But short of that, the range of potential outcomes is vast. A majority of judges might  adopt Judge Thomas Griffiths’ panel concurrence, which would have held that even if due process applied, Al Hela had been given all the process the clause would require. Alternatively, the en banc court might hold that due process should apply at Guantánamo based on the same pragmatic analysis that Boumediene applied to extend the Suspension Clause’s protections, remanding for further development of the procedural rules by the district court in the first instance. Or it might elaborate some of those details in the en banc opinion.

So long as any window for asserting procedural due process claims is left open by the en banc opinion in Al Hela, such claims would likely proceed in the district courts for a large number of the uncharged men, whether cleared or not.

Limits to the Length of Detention

The Supreme Court has made clear since its 2004 Hamdi decision that the military detention power is limited to its avowed purpose of preventing return to the relevant armed conflict. A necessary corollary is that detainees who are medically disabled from returning to the fight must be repatriated. Medical repatriation while a conflict is ongoing has long been an accepted military practice, even in the context of total war between nation states: In World War II, for example, the United States repatriated hundreds of German POWs rendered unfit to return to combat due to obvious physical disabilities (for example, a missing leg) but also due to less-visible psychological infirmities, such as shellshock.

This fundamental law-of-war principle was enshrined in the 1949 Geneva Conventions, and is codified in a multi-branch military regulation, Army Reg. 190-8, which provides for examination by a panel of medical experts  –  a “Mixed Medical Commission” (MMC) –  to establish whether a detainee’s disability is sufficient to entitle them to repatriation. In recent years, several detainees have sought to invoke this process. Shaker Aamer’s were preempted by his release to England in 2015. Two years later, a floridly schizophrenic Saudi detainee, Mohammed al Qahtani, filed a motion demanding that the government convene a Mixed Medical Commission, which his habeas judge granted. The government failed to obtain a stay from the district or appellate court, so instead, five days before the end of the Trump administration, Secretary of the Army Ryan McCarthy issued a memorandum claiming that the military regulations allowing for this neutral medical examination do not apply to anyone detained at Guantánamo. The Justice Department then moved to vacate the district court’s order. Briefing on the validity of that exemption remains pending in the district court.

Though there would appear to be serious problems with the validity of this purported last-minute regulatory change, one would assume that the same claims could be brought by directly invoking the laws of war before the habeas court. Claims for medical repatriation promise to be a significant frontier in the Guantánamo habeas litigation, given that the detainee population is now two decades older across the board, with a number of the remaining inmates already developing geriatric diseases and more still suffering from mental illnesses (some pre-existing, some provoked by or wildly exacerbated by detention). At least one other detainee has filed a petition seeking repatriation under the same process (Al-Hawsawi v. Biden, Case No. 21-cv-2907, filed in district court on Nov. 4, 2021).

Of course, more conventional challenges to the length of detention, simply asking whether the conflict against the Taliban and/or Al Qaeda is over as a factual matter, have been brought continuously over the last decade, and they should have more traction going forward, given the United States’ withdrawal from Afghanistan. At least three detainees have end-of-hostilities claims currently pending.

Finally, if the Due Process Clause does apply at Guantánamo, substantive due process may have something to say about the validity of continued detention almost 20 years on. Various habeas petitioners (including Al Hela) have already argued that the Supreme Court’s civil commitment precedents (the law governing involuntary confinement of psychiatrically dangerous individuals) establish that, as a matter of substantive due process, continuing noncriminal detention cannot be justified solely by past conduct or association, but instead requires the government to articulate a specific, present danger necessitating continued detention, supported by clear and convincing evidence. (In some respects, that is what the government’s Periodic Review Board process aims to assess, but it maintains this process is completely discretionary.) To date, in the habeas context, the danger posed by a detainee’s release has been presumed – return to the armed conflict – based on their past participation in the conflict. That presumption follows the model of traditional international armed conflicts, where detention continues until active hostilities are concluded between the warring nations because of the presumption that anyone repatriated would be drafted back into the fight.

Application of substantive due process would instead require the government to articulate the danger posed by release in an individualized, forward-looking manner, not solely rooted in past conduct. And while this could in some ways resemble the inquiry the Periodic Review Boards make, following the model of the Supreme Court’s substantive due process precedents would give detainees far greater procedural protections than are presently available in that process.


On this 20th anniversary of the prison’s opening, there are 39 men remaining at Guantánamo. It has long been clear that the 12 men currently charged before (or convicted by) military commissions represent the sum total of all detainees who will face charges. The other 27 are either cleared or awaiting re-review before Periodic Review Boards. As of January 2021, the vast majority of the uncleared-but-uncharged were united by the fact that they had been held at some point by the CIA. That no longer appears to be an absolute bar to clearance for transfer; several such men have been cleared this year after being previously denied (including, as of yesterday, the first so-called “high-value detainee” to ever be cleared, Guled Hassan Duran). Similarly, a number of men have historically failed to present well to the board owing to mental illness (whether preexisting or provoked by custody); several of them have now been cleared as well. I would anticipate that almost every one of the detainees not facing charges will be cleared before the end of this 21st year of detentions at Guantánamo.

Some of those cleared men will surely try to accelerate their transfer via the courts by making some of the arguments above. To the extent this (or some future) administration resists on the grounds that congressional transfer restrictions render it impossible to release the petitioners, the constitutionality of those restrictions will be one final frontier in the habeas litigation. Most of those transfer restrictions can be worked around if sufficient political will can be mustered within the White House. If not, questions about whether those restrictions themselves violate the laws of war or improperly trench on the President’s power to manage day-to-day military affairs may finally need to be litigated in habeas before the last man leaves Guantánamo.

IMAGE: GUANTANAMO BAY, CUBA – JUNE 25: (EDITORS NOTE: Image has been reviewed by the U.S. Military prior to transmission.) A sign reading, “Office of Military Commissions Expeditionary Legal Complex Guantanamo Bay, Cuba” stands close to where pre-trial hearings were being held for the detainees at the military prison on June 25, 2013 in Guantanamo Bay, Cuba. (Photo by Joe Raedle/Getty Images)