Later this month, the full D.C. Circuit will hear arguments in Al-Hela v. Biden, the most consequential Guantanamo habeas case since the Supreme Court’s 2008 decision in Boumediene v. Bush, which held that the Constitution’s habeas corpus guarantee applies to detainees there. The central question in Al-Hela is whether the Constitution’s Due Process Clause also applies to those detainees. As explained below, the United States’ military withdrawal from Afghanistan has made resolution of this question even more significant by placing what have so far been somewhat academic legal questions over the “war on terrorism” – and particularly over its conclusion – into sharper relief, with enormous human and political consequences.

In Al-Hela, the full D.C. Circuit appears poised to (finally) recognize that the Fifth Amendment’s Due Process Clause applies to detainees at Guantanamo. Not only were there sufficient votes on the Circuit to vacate and revisit the panel’s ruling to the contrary, but because of the change in presidential administration, the U.S. government itself no longer disputes that the Clause applies. Instead, the government argues that the Court should avoid the issue by ruling that the petitioner already received all the process he would have been due under the Constitution, including the “meaningful review” guaranteed by the Suspension Clause under Boumediene. (Besides, as Ryan Goodman has explained, the arguments in favor of the Clause’s application are overwhelming).

The government may believe it has cleverly threaded a needle here by withdrawing the Trump administration’s argument against applying the Due Process Clause to Guantanamo detainees without committing to the opposite position and, potentially, tying its own hands in future cases. But contrary to the government’s contention, application of the Clause would make a significant difference, not only in Al-Hela’s case but also in the cases of the numerous other detainees held without charge. Of the 39 prisoners remaining at Guantanamo, 27 have not been charged with any offense after nearly twenty years of captivity and instead remain in indefinite law-of-war detention, and 17 of those 27 prisoners – nearly half of the remaining detainee population – have not been recommended for transfer. (Al-Hela himself has been recommended for transfer but remains in law-of-war detention).

Since Boumediene, lower courts have sought to interpret the Supreme Court’s direction to provide “meaningful review” to habeas detainees at Guantanamo. District court judges initially interpreted this review aggressively, insisting that the government provide actual evidence that a detainee directly engaged in hostilities (here’s a notable example that highlights the tone and tenor of previous judicial skepticism of the government’s positions defending detention) and granting habeas relief in nearly sixty percent of cases. But the D.C. Circuit – led by Judge A. Raymond Randolph, who openly denounced Boumediene – drastically narrowed this review in a series of decisions. As a result, more searching judicial inquiries of the government’s allegations – of the kind Boumediene seemed to require – were replaced by deference to multiple-level hearsay statements in government intelligence reports and, most importantly, to the expansive use of ex parte evidence, which flouts principles of fundamental fairness and severely undermines the ability of detainees to meaningfully challenge the government’s allegations.

A ruling by the D.C. Circuit that the Due Process Clause applies at Guantanamo would provide an opportunity for judges to evaluate the government’s legal and factual assertions on a different basis than only under the Circuit’s narrow interpretations of the Suspension Clause. Most importantly, it would allow courts to apply doctrines of substantive and procedural due process that expose the weakness in the government’s claims of continued law-of-war detention authority – a weakness underscored by the United States’ military withdrawal from Afghanistan.

Substantive Due Process

With respect to substantive due process, the Fifth Amendment narrowly confines circumstances under which the government can imprison without trial.

There are two main exceptions to what amounts to a longstanding constitutional bar on indefinite detention by the executive without charge. The first is plainly not applicable here – civil commitment of the mentally ill. While the Supreme Court has, with controversy, permitted the expansion of this category to include sexually violent predators (who can be confined indefinitely in civil custody following completion of their criminal sentence), it upheld their confinement because they suffer from a mental illness that prevents them from controlling their actions, and not an assessment of their future dangerousness standing alone. As Justice Scalia explained in his dissent in Hamdi v. Rumsfeld, “It is unthinkable that the Executive could render otherwise criminal grounds for detention noncriminal merely by disclaiming an intent to prosecute, or by asserting that it was incapacitating dangerous offenders rather than punishing wrongdoing.”

The other main exception is the basis for all Guantanamo detentions to date – detention of combatants under the law of war. This exception has long allowed for the detention of prisoners of war (including U.S. citizens) in international armed conflicts (IACs) (i.e., conflicts between two nation states). After 9/11, the Supreme Court endorsed the detention of enemy combatants under the 2001 Authorization for Use of Military Force (AUMF) in Hamdi, also based on a non-punitive rationale – that is, the law of armed conflict has long recognized the lawfulness of detention “to prevent a combatant’s return to the battlefield.”

Notably, the Hamdi Court limited its ruling to the circumstances before it at the time. Yaser Hamdi, an American citizen, was caught fighting in Afghanistan in 2001. The Court made clear that its holding extended only to individuals who, like Hamdi, fought against U.S. or allied forces in Afghanistan while “United States troops are still involved in active combat” there. And the Court explained that such detention – like traditional prisoner-of-war detention – must end upon the cessation of hostilities (“It is a clearly established principle of the law of war that detention may last no longer than active hostilities.”) Further, Justice O’Connor, in her controlling opinion, cautioned that if the practical circumstances of the relevant conflict deviated too much from the practical circumstances of conflicts that informed the development of the law of war – i.e., conflicts where American soldiers were fighting enemy forces on a battlefield – the legal basis for the government’s detention authority could “unravel.”

Procedural Due Process

With respect to procedural due process, the Fifth Amendment generally requires rigorous, trial-like safeguards in the rare instances that it permits continued detention without charge. In the civil commitment context, the government must typically justify continued detention by, at minimum, clear and convincing evidence. Detained individuals must also typically be afforded other crucial protections such as the right to confront the government’s evidence and cross-examine its witnesses.

A ruling by the D.C. Circuit that the Due Process Clause applies at Guantanamo could be particularly impactful now because the war with the Taliban in Afghanistan – and thus the central pillar of government’s asserted law-of-war detention power – appears to be ending. If that holds, to justify continued detention, the government will need to rely on the increasingly tenuous proposition that the remaining Guantanamo detainees can continue to be imprisoned in an ongoing – and never-ending – global war against al-Qaeda.

If, as the government has argued, the prisoner-of-war detention framework referenced in Hamdi can be imported to a global NIAC against a terrorist organization, that framework still requires the continued existence of an armed conflict with active hostilities ongoing. The war in Afghanistan has long blurred the question of whether there was an ongoing conflict with al-Qaeda. Or, put another way, as long as American troops were still on the ground fighting in Afghanistan, it was easier for the government – and courts – to dodge harder questions raised by detention in a forever war against a stateless terrorist organization. But with the war against the Taliban in Afghanistan coming to an end, the government must argue that the United States remains engaged in a separate NIAC with al-Qaeda. That argument seems increasingly dubious when core al-Qaeda as it existed in 2001 has been decimated, given that IHL requires both an organized armed force and a minimum level of intensity in hostilities for the existence of a NIAC. Newer conflicts with groups that may in various ways be connected to al-Qaeda but did not attack the United States on 9/11, and did not even exist at the time, should not be seen to legally stand in the shoes of the organization against which Congress authorized force in the 2001 AUMF.

Moreover, depending on the outcome in Al-Hela, the shift from the type of “classic” battlefield detention described in Hamdi to detention in an amorphous, never-ending battlefield-less “war” should trigger significantly more rigorous procedural protections under the Fifth Amendment. These safeguards include a higher standard of proof than preponderance of the evidence, increased ability to confront the government’s evidence (including sharp restrictions on ex parte evidence), and perhaps most importantly (as I’ve argued), requiring compelling evidence that the detainee continues to pose a grave danger regardless of whether he belonged to or supported an enemy force two decades ago.

The government’s argument to the contrary – that assuming arguendo the Fifth Amendment applies, the more circumscribed habeas review outlined in Hamdi provides all the process that is due – is at odds both with international law, which supports a high bar for continued security detention in a NIAC, and with Hamdi itself, whose description of habeas review was intended for the temporary detention of enemy soldiers captured on a battlefield under firmly established law-of-war principles and not some novel form of lifelong national security detention (given the ever-evolving nature of the “armed conflict” with al-Qaeda and related groups that has no clear end in sight) that has become increasingly unmoored from those principles.

The government also maintains that whether to release a detainee based on an assessment of future dangerousness is a discretionary determination to be made by the Periodic Review Board (PRB), an Executive branch process established by President Obama in 2011 and codified in large part by Congress, and does not bear on the legality of the detention. That ten detainees, including Al-Hela himself, have been approved for transfer by the PRB and yet still remain at Guantanamo, underscores the importance of an independent judicial determination of this question, especially given the glacial pace of detainee transfers in the past.

A New Opening for a Renewed Judicial Role in Closing Guantanamo

To be sure, if the D.C. Circuit finds that the Due Process Clause applies at Guantanamo, courts are unlikely to invalidate all current detentions at Guantanamo in a single stroke, especially given the past pattern of relative judicial restraint and deference to the Executive branch. But increased judicial scrutiny of the government’s detention authority under the Constitution will increase pressure on the Biden administration to transfer detainees who have not been charged with war crimes and finally close the prison, which administration officials have said President Biden intends to do. Indeed, such scrutiny could help provide legal cover for the administration to take the necessary political steps to achieve this result. At oral argument, moreover, administration lawyers will have a new opportunity to make the right decision that they blanched at the first time in filing their brief.

More broadly, rigorous application of the Due Process Clause could help restore the basic legal principle that the U.S. government so gravely damaged after 9/11 – that law-of-war detention is a limited and temporary exception to the bedrock norm that individuals cannot be detained indefinitely without trial (no matter how dangerous they are alleged to be). Whether or not the end of the “forever” war in Afghanistan prompts courts to take meaningful steps to invalidate the “forever” prison at Guantanamo, it has certainly made the prison’s continued existence seem even more aberrational, incongruous, and, ultimately, lawless.

IMAGE: (EDITORS NOTE: Image was reviewed by the U.S. Military prior to transmission.) A prisoner paces before evening prayers at the maximum security detention center on October 22, 2016 at the U.S. Naval Station at Guantanamo Bay, Cuba. (Photo by John Moore/Getty Images)