That's what the Supreme Court will begin to tackle today, when it hears oral arguments from representatives of some of the 600 men held in Guantanamo Bay. The first issue is jurisdiction—does the Court have any over foreigners held in a foreign land in the War on Terror? From the AP report:
The Bush administration asserts the right to hold and interrogate the men as long as necessary, without formal charges or the guarantee of a trial or access to a lawyer. The administration also asserts the men are not traditional prisoners of war, who would have guaranteed rights under the Geneva Convention.