Seth Waxman, attorney for prisoners detained at Guantanamo Bay, Cuba, during oral arguments at the Supreme Court on Wednesday. (AP Photo/Lawrence Jackson)

The Guantanamo detainee cases returned to the Supreme Court Wednesday for yet another round in the longstanding battle over legal rights in the administration's "war on terror." Remarkably, the 300-plus men at Guantanamo still remain in legal limbo after six years of imprisonment. The prevailing mood among members of the Court was that enough is enough.

The third in a trio of Guantanamo cases, Boumediene v. Bush could prove the most far-reaching. It asks the simple but important question of whether the Constitution's guarantee of habeas corpus, the right to challenge your imprisonment, protects the Guantanamo detainees. In other words, the Court is being asked to draw a line in the sand: to make clear that there are certain fundamental guarantees to which these individuals are entitled, no matter what the president or Congress says. And that is exactly the message those other branches need to hear.

Ironically for such a momentous case, much of the territory the Court explored on Wednesday was familiar. In 2004, the Supreme Court ruled in Rasul v. Bush that prisoners at Guantanamo have the right to file habeas corpus petitions in federal district court challenging the lawfulness of their confinement. In so doing, the Court rejected the president's assertion that judges had no business reviewing who the United States was detaining at Guantanamo or why. The difference was that the Court decided the case under the habeas corpus statute, not the Constitution, leaving open the possibility that Congress could take action to undercut its decision.

Two years later, in Hamdan v. Rumsfeld, the Court struck down the military commissions established by executive fiat to try the handful of Guantanamo detainees charged with war crimes. (The rest of the detainees were all being held indefinitely without charge as "enemy combatants.") The Court also ruled in Hamdan that all detainees were protected, at a minimum, by Common Article 3 of the Geneva Conventions, which prohibits torture and other abuse as well as any trial that is not conducted by a "regularly constituted court affording all the judicial guarantees which are recognized as indispensable by civilized peoples." Once again, however, the Court based its ruling on federal statutes, not the Constitution.

So, while both Rasul and Hamdan made clear that the Guantanamo detainees had legal rights and access to the federal courts to enforce them, they each prompted legislative action. After each case Congress passed a new law seeking to undo the Court's decision. The most recent law, the Military Commissions Act of 2006, repealed the right to habeas corpus for Guantanamo detainees, threatening to knock all pending cases out the federal courts. The question before the Supreme Court Wednesday was whether Congress violated the Constitution by impermissibly suspending that right.

The answer is complicated by the existence of an alternative review mechanism created by Congress and the administration to serve in place of habeas corpus. This mechanism has two parts: a summary military hearing before a Combatant Status Review Tribunal (CSRT), followed by limited appellate review under the 2005 Detainee Treatment Act (DTA). The Court's prior jurisprudence suggests that Congress can eliminate habeas corpus as long as it provides an "adequate and effective substitute" -- in other words, another way of accessing the courts that is commensurate with habeas.

This means that for the Guantanamo detainees to prevail in Boumediene, the Supreme Court must find not only that the detainees are protected by the Constitution's guarantee of habeas corpus but also that the DTA-CSRT falls short of what habeas requires.

The Court will likely rule for the detainees on the first question in Boumediene for a simple reason: It already found the preconditions for a constitutional entitlement to habeas corpus three and a half years ago in Rasul. In particular, the Court explained that the Guantanamo detainees fell within the class of individuals who had for centuries been protected by the writ of habeas corpus because they were being imprisoned without charge in territory under the exclusive, complete, and permanent control of the state. That common law principle emerged in response to the actions of English kings and has been enshrined in America's Constitution since its founding.

Moreover, to conclude otherwise would invite the kind of abuses of executive power the framers of the Constitution abhorred. It would sanction the creation of more Guantanamos -- law-free zones that lack any check on the state's power to imprison, to torture, or even to kill.

To be sure, Justice Antonin Scalia, who dissented in Rasul, repeated his mantra that habeas corpus never extended to non-citizens held outside sovereign U.S. territory, not even to a place like Guantanamo, which is under complete, exclusive, and permanent U.S. control. But Scalia was refighting a battle he lost in Rasul, where Justice Anthony Kennedy concluded that Guantanamo is "in every practical respect a United States territory." Scalia's position attracted only three votes before and it did not appear to command a majority Wednesday. As in Rasul, the Court seemed moved more by the concept of law-free zones rather than formal notions of sovereignty, which the political branches could easily manipulate to put people beyond the courts.

The legitimacy of the DTA-CSRT, however, presents the Court with a new question. But it is not a difficult one. The DTA-CSRT proceedings do not even come close to replicating habeas corpus. Habeas cuts to the core of the Executive's basis to detain; the DTA-CSRT does precisely the opposite, insulating executive detention from meaningful scrutiny.

The DTA-CSRT's most egregious flaw is that it denies prisoners any real chance to challenge the accusations against them. Here's how. The CSRT starts with a presumption that every prisoner is an "enemy combatant," a determination that has already been made by the tribunal's superiors all the way up the secretary of defense and president who consistently labeled the detainees "the worst of the worst." The CSRT then reviews those prior determinations but fails to provide any of the rudiments of a fair hearing. Instead, it relies primarily on secret evidence, bars lawyers, and routinely prevents detainees from presenting evidence that would refute the accusations against them.

DTA review follows. But rather than checking the CSRT's abuses, the DTA perpetuates them. Unlike habeas, which allows a judge to hold a hearing and consider evidence (including evidence showing a person is innocent of wrongdoing), the DTA prevents any independent fact-finding. Instead, all the appeals court can do is to assess whether the CSRT followed its own rules and whether those rules are valid. That's cold comfort for men who have been locked up now for six years without a day in court. 

Several justices entertained the possibility yesterday that the Court could send the question of whether DTA-CSRT provides an adequate and effective substitute for habeas back to the appeals court to decide in the first instance. Couldn?t the appeals court make that determination, asked Justice Ruth Bader Ginsburg? They could in theory, but, as petitioners' counsel Seth Waxman explained, sending the case back to the lower court to do so now would make a mockery of the speedy and effective remedy habeas corpus has provided for centuries. "If the writ means anything," Mr. Waxman said, "it is [that] the time for experimentation is over" for these detainees at Guantanamo, who are about to enter their seventh year in isolation.

It could not be clearer that this administration will never provide the detainees at Guantanamo with a fair hearing unless the Supreme Court directly orders it to do so. Perhaps the administration has no evidence in some cases. Perhaps its evidence has been obtained through torture or other methods that would offend the values of any civilized society. Perhaps the administration is just opposed in principle to having to justify its decisions to a federal judge. Or, perhaps it's a combination of all three. But, whatever the reason, the current situation at Guantanamo is intolerable and unacceptable in any country that takes the rule of law seriously.

Habeas corpus has been one of America's strongest and proudest traditions for more than two centuries. If habeas corpus means anything, it means that individuals detained by the state must be given a fair shot at  showing their imprisonment is unlawful. There are some traditions no president or Congress should ever be allowed to break.

Jonathan Hafetz helped coordinate the filing of more than twenty friend-of-the-court briefs in Boumediene v. Bush and co-authored a friend-of-the-court brief on behalf of leading legal historians.