Gay rights campaigners want to overturn Proposition 8
A US group opposed to same-sex marriages has asked the California Supreme Court to annul thousands of gay marriages held in the state this year.
In a November referendum, voters backed Proposition 8, a measure to amend the state constitution to define marriage as between a man and a woman only.
Thousands of same-sex couples had wed after the Supreme Court ruled in June that such marriages were permissible.
A Proposition 8 campaign group says those unions should not be recognised.
The group, called Yes on 8, filed its court brief in response to several legal challenges seeking to overturn Proposition 8.
"Proposition 8's brevity is matched by its clarity," said the group's brief.
"There are no conditional clauses, exceptions, exemptions or exclusions: 'Only marriage between a man and a woman is valid or recognised in California.'"
Proposition 8 was backed by 52.1% of California voters in a referendum on 4 November, held at the same time as the US presidential election.
Supporters of same-sex marriages say the ban on such unions cannot be applied retroactively.
HAVE YOUR SAY
I don't think you can retroactively undo what a state has already done
Glen Barrington, USA
California's attorney general, Jerry Brown, also filed a brief on Friday, saying the Proposition 8 amendment was unconstitutional and deprived gay couples of a fundamental right, Associated Press news agency reported.
The Supreme Court has said it will hear the challenges to Proposition 8, but that pending its ruling, the ban on gay marriage remains in effect.
The court has said a hearing on the challenges could be held by next March.
Connecticut and Massachusetts are the only states to allow gay marriage. Several other states allow civil unions.