The President argues that he can do pretty much what ever he likes during times of war (the duration of which is, by the way, for him alone to determine). He claims this power based mainly on Article II of the US Constitution. Over the recent Christmas weekend, some Republican relatives of mine very readily accepted this explanation - without ever having actually read Article II.
Bush says it is obvious that Article II places exclusive Presidential authority in areas of national security. He argues that even Congressional limits through laws such as FISA and the Patriot Act (such as they are) are unconstitutional limits on executive authority granted by Article II. So what does it actually say? Is it a glorification of unchecked executive power?
Article I outlines the powers of Congress. Pay particular attention to section 8. In that section Congress has rather sweeping powers to interfere in exactly those areas of government Bush now claims are the exclusive domain of the executive.
To define and punish piracies and felonies committed on the high seas, and offenses against the law of nations; To declare war, grant letters of marque and reprisal, and make rules concerning captures on land and water; ...To make all laws which shall be necessary and proper for carrying into execution the foregoing powers, and all other powers vested by this Constitution in the government of the United States, or in any department or officer thereof. (Article I, section 2, paragraphs 10, 11 and 18)
In other words, there is a strong argument that Article I of the Constitution explicitly grants Congress NOT THE PRESIDENT the supreme authority in actions like the "War on Terror." And what if it is an actual war? Then Congress is the sole authority on that declaration according to Article I, section 2, paragraph 11.
Bush says he has unlimited power in times of war and with regard to the military. Yet, the Founding Fathers stated clearly in the first article of the Constitution that this is not the case!