WASHINGTON, June 18 — A passenger as well as a driver has the right to challenge the legality of a police officer’s decision to stop a car, the Supreme Court ruled unanimously today.

The ruling came in the case of Bruce E. Brendlin, who was a passenger in a car that was stopped by a deputy sheriff in Yuba City, Calif., on Nov. 27, 2001. The deputy soon ascertained that Mr. Brendlin was an ex-convict who was wanted for violating his parole. An ensuing search of the driver, the car and Mr. Brendlin turned up methamphetamine supplies.

Eventually, Mr. Brendlin pleaded guilty to a drug charge and drew a four-year prison sentence. But he continued to appeal on the issue of whether the evidence of drugs found on him resulted from an illegal search and should have been suppressed because of the Fourth Amendment’s protection against unreasonable search and seizure.

The California Supreme Court found that, consitutionally speaking, only the driver had been “seized” by the stop, and that therefore Mr. Brendlin had no basis for challenging the search that turned up the drugs. The State of California made that argument again when the case was heard before the United States Supreme Court on April 23.