A handful of Republican senators would like to determine:
(i) What is the definition of an "enemy combatant" who may be detained by the military outside the ordinary civil justice system?; (ii) What procedural rules should be employed by military tribunals?; and (iii) Which interrogation techniques should be authorized, and which prohibited?
Since these are questions the Supreme Court declined to answer in its rulings on prisoner detention, it's nice to see that other branch of government assuming a slightly less supine position--almost as if the Constitution established it as a counterweight against the executive and the judiciary.
Without delay, we have a response in the form of a Statement of Administration Policy:
If legislation is presented that would restrict the President's authority to protect Americans effectively from terrorist attack and bring terrorists to justice, the President's senior advisers would recommend that he veto the bill.
So while Bush might not (ever) be prepared to veto an omnibus spending bill, at least he's aware that he has a veto power. Let that be a lesson to anyone attempting to delineate (not even limit) the powers of the executive. Lots of analysis from Marty Lederman here; link via Andrew Sullivan.