THE U.S. COURT of appeals dropped a bombshell Friday when it ruled that the law authorizing the appointment of special prosecutors is unconstitutional. Judge Laurence Silberman, writing for himself and Judge Stephen Williams, summarizes their holding in a few sentences: "The constitutional scheme is as simple as it is complete -- Congress passes the criminal law in the first instance, the President enforces the law, and individual cases are tried before a neutral judiciary involved in neither the creation nor the execution of that law. . . . The Ethics in Government Act, it seems to us, deliberately departs from this framework in both its particular provisions and in its general purpose, which is to authorize an officer not accountable to any elected official to prosecute crimes." Judge Ruth Bader Ginsburg dissents, concluding that the act "neither impermissibly transfers an executive function to another branch nor orders an undue displacement of executive prerogatives. . . ."

The court of appeals decision is, of course, an intermediate one. No matter which way the ruling had gone, there would have been an appeal to the Supreme Court. There is still time for the high court to hear arguments and decide this critical constitutional question before the end of the term. That is fortunate, because much is at stake.

Last week's ruling comes in a case involving special prosecutor Alexia Morrison's investigation of three former Justice Department officials -- Theodore Olson, Edward Schmultz and Carol Dinkins -- in connection with congressional testimony about the government's toxic waste program. The three had refused to comply with subpoenas obtained by Mrs. Morrison, were cited for contempt of court and questioned the prosecutor's underlying authority on appeal. Mrs. Morrison is one of two special prosecutors -- the other is Whitney North Seymour, who handled the Michael Deaver case -- who refused to accept parallel appointments by the Justice Department when they were offered by Attorney General Meese last year. Thus, their authority is vulnerable to constitutional attack. This is not the case with other special prosecutors, since the Supreme Court only last week affirmed the authority of those who had accepted Justice Department backup appointments.

This case, like others -- those involving Watergate and the legislative veto, for example -- tests the system of checks and balances established by the Framers. There is also a civil liberties aspect to the litigation because the appellants contest the mechanism whereby they can be investigated and prosecuted by those who are not part of the executive branch and who are not answerable to a higher authority. Proponents of the law say it is the only practical way to make sure that justice is done in cases involving high government officials. If the court of appeals is sustained -- and a tie vote would be sufficient -- those who seek some effective way to ensure investigation and prosecution of wrongdoing at the highest levels of government will have to go back to the drawing board.