Chief Justice John Roberts, speaking for the 5-4 majority, said the private sponsors of Prop. 8 did not have legal standing to appeal after the ballot measure was struck down by a federal judge in San Francisco.
"We have never before upheld the standing of a private party to defend the constitutionality of a state statute when state officials have chosen not to," he said. "We decline to do so for the first time here."
Justices Ruth Bader Ginsburg, Stephen Breyer, Antonin Scalia and Elena Kagan joined to form the majority.
The court’s action, while not a sweeping ruling, sends the case back to California, where state and federal judges and the state’s top officials have said same-sex marriage is a matter of equal rights.
Last fall, the high court agreed to hear a last-chance appeal from the sponsors of the 2008 ballot measure that limited marriage to the union of a man and a woman.
Federal courts in San Francisco had struck down the measure on the grounds that it unfairly discriminated against gays and lesbians who wished to marry.
Usually, the governor and state’s lawyers defend state laws in federal court, but both Gov. Jerry Brown and Atty. Gen. Kamala Harris refused to defend Prop. 8.
Several sponsors of the ballot measure stepped in to defend the law, but there were questions about whether they had legal standing to represent the state in court.