California Attorney General Jerry Brown has filed court papers, urging the state Supreme Court to invalidate Proposition 8, the voter-approved measure banning same-sex marriage, it was reported yesterday.

"Proposition 8 must be invalidated because the amendment process cannot be used to extinguish fundamental constitutional rights without compelling justification," Brown said in remarks published by the Los Angeles Times.

In his court papers filed on Friday, Brown argued the Proposition 8 improperly deprives people of the right to marry -- an aspect of liberty that the Supreme Court has concluded is guaranteed by the state constitution.

Meanwhile, proponents of the measure filed court papers defending the same-sex marriage ban.

"We are confident that the will of the voters and Proposition 8will ultimately be upheld," said Andrew Pugno, general counsel forProtectMarriage.com and the Proposition 8 Legal Defense Fund.

Pugno said it was "disappointing" that Brown "has refused to defend the vote of the people as the law instructs him to."

"It will take some time to digest this new and unusual legal argument he has created," Pugno said.

Eight years ago, California voters approved Proposition 22, which specified in state law that only marriages between a man and a woman are valid in California. In May, the state Supreme Court ruled the law was unconstitutional because it discriminated against gays, and an estimated 18,000 same-sex couples got married in the ensuing months.

On Nov. 4, however, voters approved Proposition 8, which amends the state constitution to define marriage as being between a man and a woman.

In the days after the passage of Proposition 8, three lawsuits were filed directly with the state Supreme Court challenging the validity of the measure.