With Iran accused of seeking nuclear weapons and aiding insurgents in Iraq, Vice President Cheney said recently that the Bush administration is “prepared to impose serious consequences” on Iran. It would hardly be surprising if the administration were to claim that those consequences can include military action.

During the runup to the Persian Gulf War in 1991, the administration of President George H.W. Bush claimed power to attack Iraq without Congressional approval. The current administration asserted the same authority in 2002 prior to the ongoing war.

This view was wrong in 1991 and wrong in 2002. It would be equally wrong today.

Neither of the two measures earlier enacted by Congress that approve the use of force can plausibly be said to authorize an attack on Iran. The legislation enacted by Congress in 2002 authorizing use of force against Iraq permits use of force only against Iraq, not against some other country. The legislation enacted on Sept. 14, 2001, following the 9/11attacks authorizes the president to use force only “against those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001, or harbored such organizations or persons.” No serious argument has been made that Iran participated in the 9/11 attacks or is harboring people who did.

That leaves only the Constitution as a source of presidential power.

The Constitution of course gives Congress the power to declare war but assigns commander in chief responsibilities to the president. How to reconcile these overlapping and occasionally conflicting mandates has bedeviled generations of constitutional scholars. It is difficult to review the Constitution’s primary sources, however, or the full range of Supreme Court opinions or relevant historical precedents without drawing the same conclusion drawn by Abraham Lincoln — that the framers rejected the monarchical model. He said: “The provision of the Constitution giving the war-making power to Congress, was dictated, as I understand it, by the following reasons. Kings had always been involving and impoverishing their people in wars, pretending generally, if not always, that the good of the people was the object. This our convention understood to be the most oppressive of all kingly oppressions; and they resolved to so frame the Constitution that no one man should hold the power of bringing this oppression upon us.”

Chief Justice William Rehnquist, no wallflower on presidential power, shared Lincoln’s view. He said: “The example of such unlimited executive power that must have most impressed the forefathers was the prerogative exercised by George III, and the description of its evils in the Declaration of Independence leads me to doubt that they were creating their new Executive in his image.”

When there is no emergency and a significant risk of large-scale hostilities that would entail substantial casualties, use of force requires Congressional approval. The president does have a narrow, emergency power to respond to sudden attacks on U.S. armed forces located abroad. But no one contends that Iranian progress on nuclear enrichment or support for Iraqi insurgents has created an urgent threat that must be met before Congress can act. The president has time to go to Congress.

A federal district court forthrightly rejected the executive’s monarchical claims at the time of the first Gulf War in Dellums v. Bush. “If the Executive had the sole power to determine that any particular offensive military operation, no matter how vast, does not constitute war-making but only an offensive military attack,” the court said, “the congressional power to declare war will be at the mercy of a semantic decision by the Executive. Such an ‘interpretation’ would evade the plain language of the Constitution, and it cannot stand.”

The president is not possessed of the war powers of an English king of old. Before attacking Iran, the president needs Congressional approval. He doesn’t yet have it.

Michael J. Glennon is a professor of international law at the Fletcher School of Law and Diplomacy at Tufts University and former legal counsel to the Senate Foreign Relations Committee.