The Supreme Court yesterday ruled that about 500,000 members of the federal work force are barred by law from appealing if suspended for alleged misconduct.

The court, by a 5-to-3 vote, said federal employees in the "excepted service" -- those not chosen by competitive civil service tests -- are not included in a 1978 law protecting federal workers.

The decision involved a U.S. Fish and Wildlife Service employee who worked in Virginia Beach, Va. The employee, Joseph A. Fausto, was suspended for 30 days without pay in 1980 for the allegedly unauthorized use of a government vehicle. Fausto sought review with the Merit Systems Protection Board, established under the Civil Service Reform Act of 1978.

The board dismissed his appeal, saying that employees in Fausto's classification have no right of appeal to the board.

Fausto then sued the government in U.S. Claims Court, invoking the federal Back Pay Act, and a federal appeals court upheld his right to do so.

Writing for the court, Justice Antonin Scalia said Congress had made a conscious determination that "excepted service" federal employees should not be able to seek administrative or judicial review when suspended for misconduct.

In another ruling yesterday, the justices decided that courts sometimes may bar defense witnesses from testifying at criminal trials in order to punish the defendants' lawyers.

By a 5-to-3 vote, the justices upheld a Chicago man's attempted-murder conviction and 10-year sentence even though one would-be defense witness was not allowed to testify because of a defense lawyer's procedural violation.

Writing for the court, Justice John Paul Stevens said barring a witness from a trial is justified, and does not violate a defendant's fair-trial rights, if a defense lawyer's violations are aimed at gaining some tactical advantage or to hide a plan to present phony testimony.