New Haven– President Bush has told the Russians that he will withdraw from the Antiballistic Missile Treaty, which gives both countries the right to terminate on six months’ notice. But does the president have the constitutional authority to exercise this power without first obtaining Congressional consent?

Presidents don’t have the power to enter into treaties unilaterally. This requires the consent of two-thirds of the Senate, and once a treaty enters into force, the Constitution makes it part of the “supreme law of the land” just like a statute.

Presidents can’t terminate statutes they don’t like. They must persuade both houses of Congress to join in a repeal. Should the termination of treaties operate any differently?

The question first came up in 1798. As war intensified in Europe, America found itself in an entangling alliance with the French under treaties made during our own revolution. But President John Adams did not terminate these treaties unilaterally. He signed an act of Congress to “Declare the Treaties Heretofore Concluded with France No Longer Obligatory on the United States.”

The next case was in 1846. As the country struggled to define its northern boundary with Canada, President James Polk specifically asked Congress for authority to withdraw from the Oregon Territory Treaty with Great Britain, and Congress obliged with a joint resolution. Cooperation of the legislative and executive branches remained the norm, despite some exceptions, during the next 125 years.

The big change occurred in 1978, when Jimmy Carter unilaterally terminated our mutual defense treaty with Taiwan. Senator Barry Goldwater responded with a lawsuit, asking the Supreme Court to maintain the traditional system of checks and balances. The court declined to make a decision on the merits of the case. In an opinion by Justice William Rehnquist, four justices called the issue a political question inappropriate for judicial resolution. Two others refused to go this far but joined the majority for other reasons. So by a vote of 6 to 3, the court dismissed the case.

Seven new justices have since joined the court, and there is no predicting how a new case would turn out. Only one thing is clear. In dismissing Senator Goldwater’s complaint, the court did not endorse the doctrine of presidential unilateralism. Justice Rehnquist expressly left the matter for resolution “by the executive and legislative branches.” The ball is now in Congress’s court. How should it respond?

First and foremost, by recognizing the seriousness of this matter. If President Bush is allowed to terminate the ABM treaty, what is to stop future presidents from unilaterally taking America out of NATO or the United Nations?

The question is not whether such steps are wise, but how democratically they should be taken. America does not enter into treaties lightly. They are solemn commitments made after wide-ranging democratic debate. Unilateral action by the president does not measure up to this standard.

Unilateralism might have seemed more plausible during the cold war. The popular imagination was full of apocalyptic scenarios under which the nation’s fate hinged on emergency action by the president alone. These decisions did not typically involve the termination of treaties. But with the president’s finger poised on the nuclear button, it might have seemed unrealistic for constitutional scholars to insist on a fundamental difference between the executive power to implement our foreign policy commitments and the power to terminate them.

The world now looks very different. America’s adversaries may inveigh against its hegemony, but for America’s friends, the crucial question is how this country will exercise its dominance. Will its power be wielded by a single man ˜ unchecked by the nation’s international obligations or the control of Congress? Or will that power be exercised under the democratic rule of law?

Barry Goldwater’s warning is even more relevant today than 20 years ago. The question is whether Republicans will heed his warning against “a dangerous precedent for executive usurpation of Congress’s historically and constitutionally based powers.” Several leading senators signed this statement that appeared in Senator Goldwater’s brief ˜ including Orrin Hatch, JesseHelms and Strom Thurmond, who are still serving. They should defend Congress’s power today, as they did in the Carter era.

If they join with Democrats in raising the constitutional issue, they will help establish a precedent that will endure long after the ABM treaty is forgotten. Congress should proceed with a joint resolution declaring that Mr. Bush cannot terminate treaty obligations on his own. And if the president proceeds unilaterally, Congress should take further steps to defend its role in foreign policy.

We need not suppose that the president will respond by embarking on a collision course with Congress. His father, for example, took a different approach to constitutionally sensitive issues. When members of Congress went to court to challenge the constitutionality of the Persian Gulf war, President George H. W. Bush did not proceed unilaterally. To his great credit, he requested and received support from both houses of Congress before making war against Saddam Hussein. This decision stands as one precedent for the democratic control of foreign policy in the post-cold war era. We are now in the process of creating another.

*Bruce Ackerman is Professor of Constitutional Law at Yale Law School and co-author of “Is Nafta Constitutional?”