Given the elastic definition of "unlawful enemy combatant," such mistakes could morph into detention of anyone seen, rightly or wrongly, as impeding the war on terror. Whatever your assessment of George W. Bush's character, do you trust future presidents to exercise this open-ended power conscientiously and unerringly?
The Supreme Court has ruled that U.S. citizens held as unlawful enemy combatants have a constitutional right to contest their status before a "neutral decision maker." The Bush administration says a Combatant Status Review Tribunal qualifies, but so far it has been unwilling to test that argument in court. Instead it let one American detainee go and transferred the other to civilian custody for trial.
The Due Process Clause, which applies to "persons" under our government's control, does not mention nationality. When the Supreme Court ruled that non-citizens at Guantanamo have a statutory right to challenge their detention in federal court, it left open the question of whether this is also a constitutional right and, if so, whether Congress can selectively suspend it.
Since Congress has chosen to confirm the president's power grab instead of checking it, the Supreme Court will decide whether this is a country where people can be snatched off the street as enemies of the state and never be heard from again.