Let me answer your question with one of my own.
Describe to me the scenario where the president defies a Supreme Court ruling, which in today's tradition means an interpretation of the US Constitution (however wrong that interpretation might be), whereas the entire government has tacitly agreed that the Supreme Court has authority to do, and the political outcome to that president, where the other party controls the Congress and is hostile to his war power implementation?
You see, the situation is untenable for the president to get his own way here.
Now, in answer to your question, I think the Supreme Court is wrong. However, I am not in a position of power to oppose them, and I don't see how Pres Bush could get away with defying them on their ruling without impeachment.
Therefore, my original conclusion is correct; the real culprit is the US Supreme Court.
No, sir, not at all.
The real culprit, in your scenario, is the People of the United States, acting through their Representatives in Congress assembled, to impeach the President.