...[A] panel for the Fourth Circuit Court of Appeals ruled unanimously last Friday that the President "unquestionably" has the power to detain an American citizen who has taken up arms against his country. But wait. Didn't the Supreme Court say precisely that in its Hamdi decision last year? So it did, as Judge Michael Luttig notes repeatedly in his 25-page opinion penned for the court. That wasn't enough for José Padilla's attorneys, who argued that Hamdi, which concerned an American picked up on a battlefield in Afghanistan, didn't apply to their client, who was arrested domestically, at O'Hare Airport. Padilla,...