The Constitution vests the power of declaring war in Congress; therefore no offensive expedition of importance can be undertaken until after they shall have deliberated upon the subject, and authorized such a measure.

So said President George Washington in 1793. President George W. Bush thinks he knows better. He does promise to "consult" with Congress before launching a massive invasion of Iraq. And he does not rule out seeking a vote of approval. But as a matter of law, his administration claims, Bush is free to initiate a major war all by himself.

This flies in the face of the Constitution and of the Framers’ clearly expressed intent. And while Bush would hardly be the first president to usurp the war powers of Congress, launching a massive invasion of a sovereign nation without congressional authorization-despite ample time for congressional deliberation, the lack of any element of surprise, and the absence of any attack on the United States or on a treaty ally-would be the most flagrant usurpation of congressional power in the history of the presidency.

As for the reported claims by White House lawyers that Congress has already authorized an invasion of Iraq-by voting last year for a military response to the September 11 attacks and in 1991 to approve the plan to expel Iraq from Kuwait-they rest on such unpersuasive technicalities as to signal intellectual desperation.

Bush may eventually ask for a congressional vote. That would clearly be the wiser course, politically. And that’s what Bush’s father did in early 1991-notwithstanding his insistence then that he did not need congressional approval as a legal matter and his subsequent boast, "I didn’t have to get permission from some old goat in Congress to kick Saddam Hussein out of Kuwait."

But the imperial arrogance already manifested by this administration may foreshadow a damn-the-people’s-elected-representatives-full-speed-ahead approach. George W. Bush and his top people have evinced little but contempt for congressional opinion, European opinion, world opinion, or judicial opinions challenging their bold assertions of untrammeled executive power. Not to mention the opinions of whatever class of people Bush was trying to scorn with his recent crack that "most Americans don’t sit in Martha’s Vineyard, swilling white wine."

Full disclosure: I myself swilled a glass of white wine in Martha’s Vineyard this summer. But only one. Honest. And I have no bias against invading Iraq-assuming that Bush can persuade Congress that an invasion is the best way to prevent Saddam Hussein from visiting nuclear destruction upon us, contrary to the views of the military’s top brass and some of his father’s top advisers.

Given Bush’s zest for "strict construction" of the Constitution, it bears emphasizing that this often-ambiguous document is unusually clear in assigning to Congress the exclusive power to initiate foreign wars. Any ambiguity is erased by the Framers’ debates.

Article I, Section 8 assigns to Congress not only the power "to declare war," but also the powers to "grant letters of marque and reprisal, and make rules concerning captures on land and water, to raise and support armies … to provide and maintain a Navy, to make rules for the government and regulation of the land and naval forces [and] to provide for calling forth the militia to … repel invasions." Article II grants the president only the limited (albeit considerable) war powers inherent in being "Commander in Chief" of the armed forces.

Bush partisans seize upon the purported ambiguity of "declare war" and other somewhat antiquarian constitutional phrases to argue that the president may unilaterally initiate foreign wars whenever he sees fit. But the Framers’ debates, which elucidate the original meaning of the text, conclusively belie this. They show that the president may act unilaterally only to "repel sudden attacks," in the phrase of the day, and that the Framers themselves saw no ambiguities in the language they adopted.

"The Constitution … vested the question of war in the legislature," as James Madison put it. Without a single recorded exception of consequence, his colleagues agreed. Their purpose was to ensure that, in the words of James Wilson, "it will not be in the power of a single man … to involve us in" foreign wars. And that, in the words of Alexander Hamilton, the president would have "nothing more than the supreme command and direction of the military and naval forces, as first general and admiral." And that, in the words of John Marshall-as Chief Justice, in Talbot v. Seeman (1801)-"the whole powers of war [are] vested in Congress."

It is fashionable in presidential-supremacist circles to dismiss the Constitution’s allocation of war powers as a dead letter, which presidents have disregarded hundreds of times over more than two centuries and which is obsolete in today’s dangerous world. This is a vast overstatement, although an enhanced presidential role is to some extent a necessary adaptation to an age in which "sudden attacks" could involve nuclear-tipped missiles (or truck bombs) and American forces ring the globe.

While Congress has "declared" war only five times-the War of 1812, the Mexican-American War, the Spanish-American War, and World Wars I and II-there is a scholarly consensus that what the Constitution requires is not a formal "declaration" but a prior vote authorizing acts of war. And until 1950, "presidents were pretty scrupulous about ensuring that Congress had enlisted before marching the troops off to battle," in the words of John Hart Ely’s War and Responsibility.

Presidential usurpations of congressional war powers began in earnest with President Truman’s conduct of the Korean War, which Congress never clearly authorized. Those usurpations have been accompanied by congressional abdications: Many members prefer to take a stand only after seeing how a war turns out, and how the public feels about it.

But the constitutional scheme has never been smashed as irretrievably as it would be by an unauthorized invasion of Iraq. President Eisenhower vowed in 1956: "Until the Congress, which has the constitutional authority, says so … I am not going to order any troops into anything that can be interpreted as war." And while the Vietnam War is often cited mistakenly (as recently as August 28, in a New York Times editorial) as a congressionally unauthorized war, in fact the Tonkin Gulf Resolution of 1964 gave President Johnson blanket authority to (unwisely) defend South Vietnam.

Since then, Presidents Nixon (who secretly bombed Cambodia in 1969-1970), Reagan (who occupied Grenada in 1983), George H.W. Bush (who invaded Panama in 1989), and Clinton (who occupied Haiti in 1994 and bombed Kosovo and Serbia in 1999) have all usurped congressional war powers. But the Grenada and Panama operations-which succeeded militarily and thus politically-derive a tincture of legitimacy, or at least of mitigation, from the need for surprise and from the tacit recognition in the War Powers Resolution of 1973 that sometimes presidents will send troops into brief hostilities without prior authorization. Clinton’s occupation of Haiti was bloodless, and his high-altitude bombing of Kosovo and Serbia shed no American blood.

There is no precedent, therefore, for a congressionally unauthorized invasion that could not possibly be a surprise and could cost many thousands of American lives.

The Bush camp’s argument that the only vote the president needs is the joint resolution adopted three days after the September 11 attacks rests on language authorizing him "to use all necessary and appropriate force against those nations, organizations or persons he determines … aided" those attacks "or harbored" the attackers. This might make sense if the evidence of Iraqi complicity were strong. But so far, it appears shaky. For Bush to cite such non-proof as a mandate for full-scale war would smack of bad faith.

An even weaker reed is the 1991 congressional vote authorizing the first President Bush to enforce U.N. Security Council resolutions by expelling Iraq from Kuwait. The argument here is that Congress intended in 1991 to authorize a full-scale invasion of Iraq to depose Saddam if, after he was expelled from Kuwait, his conduct within Iraq’s own borders violated the terms of his surrender.

Does anyone, anywhere, really believe this? The first President Bush obtained the U.N. resolutions and the congressional authorization alike only by promising that he would not go beyond liberating Kuwait. The House underscored the point by voting overwhelmingly the same day that any invasion of Iraq proper must be explicitly approved in advance by Congress. And only Great Britain, of all the Security Council members and other nations that supported Operation Desert Storm in 1991, broadly supports the Bush position now.

The policy question posed by Saddam’s Iraq is a difficult one. The legal question is not a close call. George Washington was right. George W. Bush is wrong.