President Bush seems to have it right that the 1972 Anti-Ballistic Missile Treaty stands in the way of the National Missile Defense that he is determined to build. But he seems to underestimate the difficulties of getting around the pesky agreement.

The treaty, signed and ratified by the United States and the Soviet Union, clearly prohibits either nation from going forward with a national missile defense system. The two parties agreed that “effective measures to limit anti-ballistic missile systems should be a substantial factor in curbing the race in strategic offensive arms and would lead to a decrease in the risk of outbreak of war involving nuclear weapons.” So they pledged that neither nation would “develop, test or deploy” ABM systems or components except one local system each around their respective capitals, Washington and Moscow.

Advocates of an American missile defense system have pressed hard to make the ambitious project sound necessary and practical. Hardly anyone ridicules it as Star Wars anymore. Some advocates have argued that the treaty is dead because the Soviet Union no longer exists. But established international law holds that when a party to a treaty reorganizes or splits up the agreement remains binding on the “successor states.”

The United States and successor states the Russian Federation, Ukraine and the Republic of Belarus met at Geneva in 1993 for the fourth five-year review of the 1972 treaty and “reaffirmed” their commitment to the pact. Similarly, Secretary of State Madeleine Albright met in New York in 1997 with representatives of the Russian Federation, Ukraine, Belarus and Kazakhstan and agreed that the 1972 treaty would remain binding on all parties when their joint memorandum had been ratified.

Although the United States has not ratified that 1997 memorandum, Secretary of State James Baker, speaking for the first Bush administration and the U.S. government, said after meeting with Russian President Yeltsin in 1992: “I made the point to President Yeltsin that the United States remains committed to the ABM Treaty.”

Simply ignoring the treaty appears to be out of the question. The United States cannot afford to walk away from its solemn commitments. That leaves as the only option invoking Article XV of the treaty. The language is explicit and drastic:

“l. This Treaty shall be of unlimited duration.

“2. Each Party shall, in exercising its national sovereignty, have the right to withdraw from this treaty if it decides that extraordinary events related to the subject matter of this Treaty have jeopardized its supreme interests. It shall give notice of its decision to the other Party six months prior to withdrawal from the Treaty. Such notice shall include a statement of the extraordinary events the notifying Party regards as having jeopardized its supreme interests.”

It will be interesting to see what “extraordinary events” are to be accused of jeopardizing U.S. “supreme interests.” Officials in the White House, Pentagon and State Department have their work cut out for them if they try to draft such a statement now that the Cold War is over and the missiles no longer point at each other.