THERE WAS NOTHING surprising about the way in which the Supreme Court disposed of the Iranian assets case. By deciding the legal issues no narrowly that their resolution will have little effect on other situations, the justices avoided the unnecessary broadening of presidential powers. At the same time, they upheld the power of the president to find extraordinary solutions to critical international problems at least as long as Congress acquieces. Any other decision would have raised grave doubts abroad about the authority of American presidents in international negotiations or the good faith of the American government in carrying out its commitments.

In the long run, this decision could be an expensive one for American taxpayers. That's because the court made clear that the corporations and businessmen who claim Iran owes them money can sue the U.S. government -- although it is not certain they will win -- if their claims aren't satisfactory disposed of elsewhere. Whether that happens or not depends to a large extent on the good faith with which the government of Iran carries out the commitments it made last January.

The effect of the agreement under which the hostages were released was to free Iranian assets in this country and to transfer the legal claims businessmen had against the Iranian government to a special international tribunal. That tribunal was given a fund of $1 billion to pay the debt and damage claims it finds justified, and the Iranian government agreed to provide more money if more is needed.

In theory, the arrangement should make the businessmen whole. If it doesn't, if Iran fails to produce additional funds upon demand, the businessmen will be back in American courts trying to collect their money from Uncle Sam. In that sense -- and this is critical to the ease with which the justices disposed of the case -- the businessmen are in no worse shape, and in some ways are better off, than they would have been if the agreement had not been signed.

Once the hostages were released, there was -- and there probably still is -- a strong temptation for the American government to repudiate the rest of the agreement; it was, after all, made under duress. The Supreme Court could have accomplished the same end by ruling that the agreement violated American law. But by resisting that temptation and now by the court's decision upholding President Carter's authority to act as he did, the country has escaped from this terrible incident with at least its reputation for keeping its word intact.