The only thing the Three Mikes did know beyond a reasonable doubt was that the legality of water-boarding has nothing to do with international treaties, secret legal memos, acts of Congress, or their personal interpretations of same. The claim on which they were all perfectly clear is that the legality of future torture will be determined by the president and the attorney general as the occasion arises. It will not be measured by any objective standard of conduct but will turn on "the circumstances" surrounding them (in McConnell's formulation) or the value "of the information you might get" (in Mukasey's). It will be a secret decision, made using shifting, subjective standards, for which neither the torturers nor the legal decision-makers will ever be held to account.
This is not simply the theory of a unitary executive at work; this isn't the notion that the president makes the law, and acts of Congress are legal elevator music. This vision of executive power is that the law not only emanates from the president but also ebbs and flows with his hunches, hopes, and speculations, on a moment-to-moment basis. What we are hearing now from senior Bush administration officials is that if the president thinks someone looks kinda like a terrorist and the information sought from him seems kinda worth getting, it will be legal to torture him. And it's legal no matter who justified it, regardless of the supporting legal doctrine, because, well, the president just had a feeling that the information would prove valuable.
That's not an imperial presidency. That's the kind of presidency Yahweh might establish. I'm sure there's some law professor out there who can make the legal argument that executive power in wartime encompasses even the reckless guesses and impressionistic whims of a single man, as they arise. At which point, that too will become an "open question" on which "reasonable people will differ." And the dance will begin again.