ATTORNEY GENERAL William French Smith may or may not be right in his belief that the special prosecutor law is constitutionally defective. Other lawyers have reviewed this act, which requires that these prosecutors be appointed when high officials are accused of crime, and they have come to a contrary opinion. But having put his "serious reservations" about the law on the record, Mr. Smith should now tell Congress how it can correct the defects he believes he has found.

Such recommendations from the attorney general would force Congress to face the basic question he has raised: Can the power to enforce the criminal law be lodged in some cases in an official who is not part of the executive branch? Mr. Smith contends that by placing the appointment of special prosecutors in the hands of federal judges and by making them unaccountable to and untouchable by the president, the act unconstitutionally splinters the president's authority to enforce the law. If he is right, an entirely different approach will have to be taken to the problem of crime and corruption in high office.

It would be inappropriate for Mr. Smith to leave the situation the way it is, as some Department of Justice officials have suggested he may, on the ground that the law comes up for automatic review in 1983. The odds are that Mr. Smith will have to act under its provisions before that time. No attorney general should have to trigger a complicated mechanism that he believes is unconstitutional unless his view has been carefully considered -- and rejected -- on Capitol Hill. Besides, Mr. Smith has opened the way for a major court battle anytime a special prosecutor decides to take a case to trial.

Even if Congress were to decide that Mr. Smith's fears were misguided, a thorough review of the special prosecutor law would be useful. It has been invoked twice since it was passed in 1978. Each time, the matter involved seemed originally to be -- and, in fact, was -- too trivial for such a fearsome weapon of justice. Each involved minor charges of drug use by White House aides, and each was dropped without prosecution by the special prosecutors.

In the one instance during the Carter administration when a special prosecutor might have been useful, the law didn't fit the facts. That was Billy Carter's frolic with the Libyans and its aftermath. The law doesn't authorize a special prosecutor to look into activities such as his, and no one ever made the kind of allegation against a high official necessary to trigger the law's provisions.

These three situations provide the kind of experience that was lacking when Congress wrote the special prosecutor statute. There is no need for Congress to wait for more examples before reexamining the mechanism it invented. By raising doubts about the legitimacy of the whole arrangment, the attorney general has lent an aspect of urgency to that examination.