THE REAGAN administration made a tactical error by contending legalistically that the International Court of Justice had no jurisdiction to hear Nicaragua's complaint of American aggression. For the World Court, built on a United Nations design, is essentially a political body. No other case having to do with the use of force or a threat to the peace has ever come before it: these have always been accepted as political questions to be dealt with elsewhere. Given the David vs. Goliath aspect of this matter, however, it would have been only prudent to anticipate that the court might choose to hear the case. This it has now done, putting the United States in the uncomfortable position of appearing reluctant to be brought before international justice.

This leaves the administration with two things to do. First, it should openly accept the political nature of the forum and stoutly defend American national interests within it. The American policy is not particularly popular even among friends in Western Europe, whose judges were among those rejecting the American no-jurisdiction claim. Still, this country is not without a serious case. It can argue in the Hague, as it has argued at the United Nations and in other forums, that the respect for law contemplated by the United Nations Charter is a two-way street: Nicaragua must be expected to stop its depredations against its neighbors, if the United States is expected to halt the measures it insists it takes for collective self-defense. Surely the Reagan administration has enough confidence in its policy to carry it to the Hague.

Meanwhile, something further has to be done about the CIA operations that are at the heart of Nicaragua's complaint: they should be stopped, finally and permanently. The purpose is not to get right with the World Court but to lift a burden from American policy. Nicaragua, scene of so many past American interventions, simply is not the right place to sustain this one. Support of the contras gets in the way of the other means -- aid and diplomacy -- available to the administration to fulfill American obligations to friends in Central America and to shift the struggle in the region toward more peaceful channels.

Committed as it is, the administration may not be ready to end the program for which it is being stung in world opinion. But there are other reasons to end it, and as it happens, the odds are strongly against congressional renewal of the requisite funding. A mooting of the case by this means would be a good idea.