When ships of the U.S. Sixth Fleet sailed into the Gulf of Sidra last month, White House spokesmen treated the episode as a police action carrying two messages. The first was that international law prohibits exclusionary zones such as Muammar Qaddafi's "line of death." The second, implicit in the deadly vigor with which the first was delivered, was that terrorism is an impermissible violation of international norms.

When a squadron of U.S. bombers struck Libyan terrorist support facilities several weeks later, the president again invoked an international norm in justification: the self-defense provisions in Article 51 of the United Nations Charter.

It is not surprising that this country, after long provocation, should act as the avenging instrument of abused international law. From the early 19th century, when President Madison sent U.S. Marines against the Barbary pirates, the United States has championed international norms, which in turn have served American interests in global stability. What is surprising is that the same country that defends international law against terrorism -- and exhorts others to do so -- is now violating it at the United Nations.

As a result of congressional cuts topped off with additional trimming by administration budget cutters, the United States will reduce its contribution to the U.N. this year by at least 40 percent -- roughly $80 million -- and in so doing violate its international legal commitments under the U.N. Charter. Defenders of the U.S. cuts argue that they will force the world body to give this country influence commensurate with its 25 percent share of U.N. costs and that in any event the U.N. cannot receive special treatment at a time of belt-tightening for the entire federal budget.

They are missing the point. United Nations dues are not determined by unilateral action. They are apportioned according to a negotiated formula anchored in Article 17, a binding provision of the U.N. Charter, and based upon members' gross national products. By no means, however, does the existence of Article 17 permanently shackle this country to payment of any particular percentage contribution. On the contrary, at U.S. urging, the General Assembly has already reduced the United States' share of the bill on three occasions in the past. If the American people want it lowered again -- by whatever amount -- there is a procedure for negotiating it down that would not violate, and thus weaken, the U.N. Charter.

But the legal course has been ignored. Ironically, in their collective resort to illegality, Congress and the administration have injured this country's stature and credibility as a defender of international law at precisely the time we are exhorting others to join in its defense against terrorism. That is a double standard that should be disquieting to U.S. policy makers.

First, as a delegation of European ambassadors pointed out to Deputy Secretary of State John Whitehead, the casual disregard of U.S. treaty obligations in one case tends to debase the value of our signature on any treaty. After all, the United States is party to numerous treaties and legal commitments that are vital to our national interests -- the NATO Pact, the Convention on Civil Aviation, the Nuclear Non-Proliferation Treaty, various bilateral and multilateral treaties governing extradition, the network of friendship, commerce and navigation treaties that protect and promote U.S. trade and investment abroad, and many others. Do we really want to have to explain to our allies and fellow signatories when our word is good and when we might be winking?

Second, it is worth reminding ourselves that the very norms the United States sought to defend by its actions in the Gulf of Sidra, Tripoli, and Benghazi derive their legal standing from their status in a U.N. agreement. For the Gulf of Sidra example, the source is the Law of the Sea Treaty, whose provisions on the definition of a bay on international rights of overflight and navigation and on the 12-mile territorial limit, give these principles a legal stature. For the strikes against Tripoli and Benghazi, the relevant source is the U.N. Charter itself, whose Article 51 protects the "right of individual or collective self defense."

Finally, before overturning Article 17, let us also remember one more thing. It was the United States which for many years insisted upon the binding application of this provision: first against countries that, like the U.S.S.R., continue to refuse payment for some U.N. peacekeeping activities and for technical assistance to developing countries; and more recently, against member states that are chronically late with their dues. In a 1962 proceeding before the World Court, the United States argued: "The legal consequence of the General Assembly assessment resolution . . . was to create binding legal obligations of member states" -- an opinion reaffirmed by the legal adviser to the State Department in 1975 and again in 1978.

Ultimately, the choice faced by the United States is starkly simple: we abide by our treaties or we don't. If Congress wants to change the terms of a treaty, the legal recourse is to renegotiate. If negotiation fails, then other methods may be considered. But to throw our legal commitments to the winds is to invite others to do the same or, as in the case of the Soviet Union, to condone their having done so.