People get nervous when the president says a la Richard Nixon,"when the president does it, that means that it's not illegal." And that is the theory behind many of the legal innovations we've been arguing about since 9/11. What the Bush White House has offered is essentially the Nixonian view of the Constitution, albeit with less sweating and twitching. But recognizing that people get a little queasy about this argument, they've moved"Congress authorized it" front and center. The argument is that the Authorization for the Use of Military Force passed before the war in Afghanistan,"all necessary and appropriate force" etc against Al Qaeda, voids (as they've said at one time or another) FISA, the Non-Detention Act, the Posse Comitatus Act, you name it. All of which is news to the people who voted for it.
But what a red herring when you consider their view that the president needs no authorization whatever to launch a war whenever he feels its necessary. They're not really saying Congress added to his power with the AUMF. Congress couldn't have added to his power. The AUMF has all the legal effect of a hortatory resolution from Congress declaring it international nurse's week. In their theory, the president already had the power to go to war with whomever he wanted. The president's leading theorist of the war power writes unabashedly of "the president's right to start wars." So these powers are incident to wartime. And the president gets to say when it's wartime.