Look, whomod, you do realize that lawyers often disagree about how to interpret cases, right? That, in fact, is why we have judges.
So the mere fact that the ACLU, which has their own legal philosophy, disagrees with someone in the Justice Department is not, itself, dispositive of anything other than a dispute on an unsettled area of law.
The fact of the matter, as discussed a number of times in the past, is that there is a legitimate question as to the powers of a president during a military action and, especially, as against a foreign combatant. You can disagree with the Bush administration if you want, that's your right, but the fact a liberal special interest group shares your view is no more dispositive than if, say, the NRA agrees with me on gun control.