Robert Chesney, Who May Be Held? Military Detention Through the Habeas Lens, 52 B.C. L. Rev. (forthcoming 2011) (via SSRN). Here's the abstract in part:
We lack consensus regarding who lawfully may be held in military custody in the contexts that matter most to U.S. national security today—i.e., counter-terrorism and counterinsurgency. More to the point, federal judges lack consensus on this question. They have grappled with it periodically since 2002, and for the past three years have dealt with it continually in connection with the flood of habeas corpus litigation arising out of Guantanamo in the aftermath of the Supreme Court's 2008 decision in Boumediene v. Bush. Unfortunately, the resulting detention jurisprudence is shot through with disagreement on points large and small, leaving the precise boundaries of the government's detention authority unclear.
The survey concludes that something close to consensus has emerged regarding the use of group membership as a sufficient condition for detention, but that there may yet be considerable disagreement as to what counts as membership in this context. The survey also notes that the jury remains out with respect to whether non-member support for certain groups may also function as a sufficient condition for detention. With respect to variables that can function as constraints on detention authority, the survey shows that the courts have developed consensus against employing certain constraints (such as forbidding the use of detention as to citizens, or in circumstances where the government might have a criminal prosecution alternative). On the other hand, the question of geographic constraints on the scope of detention authority remains unsettled.