Justice Anthony M. Kennedy said yesterday that he will not be voting in a case challenging the constitutionality of the law establishing independent counsels to investigate wrongdoing by senior government officials.

Kennedy declined to say why he was dropping out of the case, but his move leaves open the possibility that one of the most controversial cases to come before the court in recent years will be decided on a tie vote.

Tie votes at the high court set no precedent but automatically leave intact the lower court's ruling. In this case, a 4-to-4 vote would leave standing a divided D.C. federal appeals court panel decision last month striking down the law as unconstitutional. That decision came in a case involving independent counsel Alexia Morrison's investigation of former assistant attorney general Theodore B. Olson for allegedly lying to Congress.

Orders released Monday by the court indicated that Kennedy had not participated in the court's decision to hear Morrison's appeal, but it was not certain that Kennedy was permanently out of the case. The high court is scheduled to hear oral arguments April 26.

A 4-to-4 deadlock would shut down Morrison's investigation and likely overturn the perjury conviction in December of former White House aide Michael K. Deaver.

It also would jeopardize the Feb. 11 illegal-lobbying conviction of former White House political director Lyn Nofziger and the Iran-contra investigation by independent counsel Lawrence E. Walsh. Although Walsh and Nofziger's prosecutor, James C. McKay, received backup appointments by Attorney General Edwin Meese III, both began collecting evidence before the appointments and may face obstacles in using some of that information.

There is no Supreme Court rule regarding when justices should refrain from hearing certain cases, though the American Bar Association's Code of Judicial Conduct says judges should recuse themselves whenever their impartiality "might reasonably be questioned." Judges most often recuse themselves when they or close family members have a personal, professional or financial relationship with one of the parties in a case or with one of the lawyers in a case.

There is no rule on whether justices need reveal their reasons for not sitting. Chief Justice William H. Rehnquist and Justices Harry A. Blackmun and Sandra Day O'Connor routinely say why they are not voting in cases while other justices generally do not state their reasons, according to a court spokeswoman.

Kennedy's decision may have been prompted by a perceived problem with the Olson case or with any of the other three investigations.

Kennedy was a Sacramento, Calif., lawyer who did some work for Ronald Reagan when he was governor of California, and Deaver, Nofziger and Meese were all key aides to Reagan then. Kennedy may feel that his relationship with them or especially with Meese, who is under investigation by McKay, may be such that he would feel it necessary to excuse himself.