Wesley K. Clark and Kal Raustiala note an inherent contradiction in treating terrorists as “enemy combatants”:

Labeling terrorists as combatants also leads to this paradox: while the deliberate killing of civilians is never permitted in war, it is legal to target a military installation or asset. Thus the attack by Al Qaeda on the destroyer Cole in Yemen in 2000 would be allowed, as well as attacks on command and control centers like the Pentagon. For all these reasons, the more appropriate designation for terrorists is not “unlawful combatant” but the one long used by the United States: criminal.