If transferred to the United States, detainees may be able to seek judicial review over a broader range of actions taken against them. Besides eliminating detainees' access to habeas corpus review, the DTA and MCA stripped federal courts of jurisdiction to hear most claims by noncitizen detainees. Specifically, federal courts are denied jurisdiction over "any other action against the United States or its agents relating to any aspect of the detention, transfer, treatment,
trial, or conditions of confinement of an alien who is or was detained by the United States and has been determined by the United States to have been properly detained as an enemy combatant or is awaiting such determination."

Although the Boumediene Court held that the constitutional writ of habeas permitted Guantanamo detainees to challenge the legality of their detention, the Court declined to "discuss the reach of the writ with respect to claims of unlawful conditions of treatment or confinement." Because the Boumediene Court left these questions unresolved, the viability of measures stripping courts of jurisdiction to hear claims regarding the conditions of detention may depend upon a reviewing court's interpretation of the constitutional protections owed to detainees. While measures that eliminate detainees' ability to pursue statute- or treaty-based challenges to aspects of their detention may be deemed permissible by a reviewing court, measures that seek to eliminate (rather than merely circumscribe) detainees' ability to bring constitutional challenges regarding the circumstances of their detention would likely be subject to serious legal challenge. Although the scope of constitutional protections owed to Guantanamo detainees remains a matter of legal dispute, it is clear that the procedural and substantive due process protections of the Constitution apply to all persons within the United States, regardless of their citizenship. Accordingly, detainees transferred to the United States might be able to more successfully pursue legal challenges against aspects of their detention in the United States that allegedly infringe upon constitutional protections owed to them.

SNIP

While many persons currently held at Guantanamo are only being detained as a preventive measure to stop them from returning to battle, the United States has brought or intends to pursue criminal charges against some detainees. Various constitutional provisions, most notably those arising from the Fifth and Sixth Amendments to the U.S. Constitution, apply to defendants throughout the process of criminal prosecutions. Prosecuting Guantanamo detainees inside the
United States would raise at least two major legal questions. First, does a detainee's status as an enemy belligerent reduce the degree of constitutional protections to which he is entitled?

Secondly, would the choice of judicial forum--that is, civilian court, military commission, or court-martial--affect interpretations of constitutional rights implicated in detainee prosecutions?

As previously discussed, the nature and extent to which the Constitution applies to noncitizens detained at Guantanamo is a matter of continuing legal dispute. Although the Supreme Court held in Boumediene that the constitutional writ of habeas extends to detainees held at Guantanamo, it left open the nature and degree to which other constitutional protections, including those relating to substantive and procedural due process, may also apply. The Boumediene Court noted that the Constitution's application to noncitizens in places like Guantanamo that are located outside the United States turns on "objective factors and practical concerns." The Court has also repeatedly recognized that at least some constitutional protections are "unavailable to aliens outside our geographic borders." The application of constitutional principles to the prosecution of aliens located at Guantanamo remains unsettled.

On the other hand, it is clear that if Guantanamo detainees are subject to criminal prosecution in United States, the constitutional provisions related to such proceedings would apply. The application of these constitutional requirements might nevertheless differ depending upon the forum in which charges are brought. The Fifth Amendment's requirement that no person be held to answer for a capital or infamous crime unless on a presentment or indictment of a grand jury, and the Sixth Amendment's requirements concerning trial by jury, have been found to be inapplicable to trials by military commissions or courts-martial. The application of due process protections in military court proceedings may also differ from civilian court proceedings, in part because the Constitution "contemplates that Congress has `plenary control over rights, duties, and responsibilities in the framework of the Military Establishment, including regulations,
procedures, and remedies related to military discipline.'" In the past, courts have been more accepting of security measures taken against "enemy aliens" than U.S. citizens, particularly as they relate to authority to detain or restrict movement on grounds of wartime security. It is possible that the rights owed to enemy belligerents in criminal prosecutions would be interpreted more narrowly by a reviewing court than those owed to defendants in other, more routine cases, particularly when the constitutional right at issue is subject to a balancing test.

Shorter version:  there is no clear cut rule that says the detainees, as non-citizens who are not on American soil, enjoy all the constitutional protections that would attach the moment they come here.  There's still many legal arguments either way, but it hasn't been resolved (and the author of The Guardian piece gets a few things wrong, and the Op-ed in the Washington Post to which he points, written by former a WH counsel and special envoy to Guantanamo) make compelling legal arguments, but not ones that are absolute.