Bush has cited two grounds for flouting the will of Congress, or of unilaterally expanding presidential powers. One is the claim of the "inherent" power of the commander in chief.

Second is a heretofore obscure doctrine called the unitary executive, which gives the president power over Congress and the courts. The concept of a unitary executive holds that the executive branch can overrule the courts and Congress on the basis of the president's own interpretations of the Constitution, in effect overturning Marbury v. Madison (1803), which established the principle of judicial review, and the constitutional concept of checks and balances.

The term "unitary government" has two different meanings: one simply refers to the president's control of the executive branch, including the supposedly independent regulatory agencies such as the SEC and the FDA. The other, much broader concept, which is used by Bush, gives the executive power superior to that of Congress and the courts. Previous presidents have asserted the right not to carry out parts of a bill, arguing that it impinged on their constitutional authority; but they were specific both in their objections and in the ways they proposed to execute the law. Clinton, for example, objected to provisions in a bill establishing a semi-autonomous National Nuclear Security Administration, which set out the reasons for removing the director. Clinton objected that that impinged on his presidential prerogatives. Bush asserts broad powers without being specific in his objections or saying how he plans to implement the law. His interpretations of the law, as in his "signing statement" on the McCain amendment, often construe the bill to mean something different from ?and at times almost the opposite of?what everyone knows it means.

The concept of the unitary executive, which has been put forward in conservative circles for several years, has been advocated mainly by the Federalist Society, a group of conservative lawyers who also campaign for the nomination of conservative judges. The idea was seriously considered in the Reagan administration's Justice Department. One of its major supporters was Samuel Alito, then a lawyer in the Justice Department. In his confirmation hearing, Alito said that the memorandum he wrote saying that the president's interpretation of a bill "should be just as important as that of Congress" was "theoretical." But no president until Bush explicitly claimed that the concept of a unitary executive was a basis for overruling a bill.

The theory was formulated by John Yoo, a mid-level but highly influential attorney in the Justice Department between 2001 and 2003, who took the view that the president had the power to do pretty much whatever he wanted to do. (He also wrote the infamous memorandum defending what amounted to torture.) As White House counsel, Alberto Gonzales, now attorney general, also publicly supported the theory of the unitary executive.

The theory rests on the Oath of Office, in which, according to the Constitution, the newly elected president promises to "faithfully execute the office of President," and also on the section of Article II that states that the president "shall take care that the laws be faithfully executed." The administration has put forward unprecedented interpretations of both clauses, claiming that they give the president independent authority, unchecked by the other branches of government, to decide what the law means. This theory overlooks the fact that the framers were particularly wary of executive power. A number of constitutional scholars I have spoken with describe the administration's theory of the unitary executive as no more than a convenient fig leaf for enlarging presidential power.