Bigdog wrote: "[Islamic terrorists] are unprivileged combatants..."
"Unprivaleged" or "Unlawful" combatants are denied the status of lawful combatants by the Geneva Conventions and are subject to domestic law. That is, they are criminals and not soldiers accorded the special protections and privileges of soldiers.
Civil criminal justice applies here for many reasons, not the least of which is that to confer the status of combatant on Islamic terrorist is to confer legitimacy on the sovereign power under whose orders they operate. Ultimately, the sovereign power is the one held responsible for the illegal actions (war crimes) committed by its soldiers (although they can individually be held accountable for their illegal actions, too)