I want to add a small addendum to your post . There is a big difference between the president asking for a power and Congress granting it to him, and the president claiming a power for himself and Congress acquiescing. Critics of the Bush administration argue that Bush shot himself in the foot by failing, in the immediate aftermath of 9/11, to ask Congress for powers that it would have been happy enough to give him. Bush (or Cheney or Addington or whoever) supposedly refused to take this step because he (or they) didn't just want to obtain additional powers for counterterrorism activity; they also wanted to establish a precedent that the executive had the inherent or constitutional power to engage in these activities, at least in wartime, without congressional authorization. This would give the executive the power and flexibility it would need to address future threats, including and especially those not foreseen by Congress and hence not anticipated in existing law, and help restore the imperial presidency that was lost after Watergate.
The recent FISA amendment bill vindicates this strategy. Henceforth, presidents who contemplate law-breaking for national security purposes will look back to the Bush administration and see that the president got away with these activities, and indeed received the blessing of Congress-even in the most unpropitious political atmosphere imaginable. Private actors such as telephone companies will also in future look to this precedent, when they weigh the risks of defying the president versus the risks of defying Congress.
To be sure, Congress does not explicitly acknowledge the president's small-c constitutional new powers, and Congress tries to anticipate this behavior by providing in the new bill that the FISA procedure will be the "exclusive" means for surveillance. However, this is akin to stating that a precedent is not a precedent. Looking forward, presidents and private actors should anticipate the following, if they again break the surveillance law. (1) A great deal of political noise. (2) A bill that implicitly excuses them for what they have done. (3) And, in that same bill, a provision that further tells them not to do it again. I think they can live with that.
The critics, careful lawyers that they are, understood that Bush would have a stronger legal case for his counterterrorism policies if they had congressional imprimatur. But the critics simply did not share his other goal-which was to strengthen presidential power, which requires the president to defy Congress and then face it down. This, Bush has done. And it may be his most important legacy-a grand success for Cheney, Addington, Yoo, and the other presidential-power supporters in the administration.