SAN FRANCISCO - The California Supreme Court voided the nearly 4,000 same-sex marriages sanctioned in San Francisco this year and ruled unanimously Thursday that the mayor overstepped his authority by issuing marriage licenses to gay and lesbian couples.

The court said the city violated the law when it issued the certificates, because both legislation and a voter-approved measure defined marriage as a union between a man and woman.

The justices separately decided with a 5-2 vote to nullify the marriages that were performed from Feb. 12 to March 11, when the court halted the weddings. Their legality, Justice Joyce Kennard wrote, must wait until courts resolve the constitutionality of state laws that restrict marriages to opposite-sex couples.