But Brown said he reached a different conclusion "upon further reflection and a deeper probing into all the aspects of our Constitution."
"It became evident that the Article 1 provision guaranteeing basic liberty, which includes the right to marry, took precedence over the initiative," he said in an interview Friday night. "Based on my duty to defend the law and the entire Constitution, I concluded the court should protect the right to marry even in the face of the 52 percent vote."
Brown, who served as governor from 1975 to 1983, is considering seeking the office again in 2010. After California voters passed Proposition 8 on Nov. 4, Brown said he personally voted against it but would fight to uphold it as the state's top lawyer.
The litigation over Proposition 8 is shaping up, Brown said, as a high-stakes conflict between the electorate's right to direct democracy and rights of minorities to equal treatment.
Brown submitted his brief in one of the three legal challenges to Proposition 8 brought by same-sex marriage supporters. The measure, a constitutional amendment that passed with 52 percent of the vote, overruled the Supreme Court decision last spring that briefly legalized gay marriage in the nation's most populous state.
Shannon Minter, legal director of the National Center for Lesbian Rights, called the attorney general's change of strategy "a major development."
"The fact that after looking at this he shifted his position and is really bucking convention by not defending Prop. 8 signals very clearly that this proposition can not be defended," Minter said.
The sponsors of Proposition 8 on Friday argued for the first time that the court should undo the marriages of the estimated 18,000 same-sex couples who exchanged vows before voters banned gay marriage at the ballot box last month.
The Yes on 8 campaign filed a brief telling the court that because the new law holds that only marriages between a man and a woman are recognized or valid in California, the state can no longer recognize the existing same-sex unions.
"Proposition 8's brevity is matched by its clarity. There are no conditional clauses, exceptions, exemptions or exclusions," reads the brief co-written by Kenneth Starr, dean of Pepperdine University's law school and the former independent counsel who investigated President Bill Clinton.
Both Brown and gay rights groups maintain that the gay marriage ban may not be applied retroactively.
The Supreme Court could hear arguments in the litigation as soon as March. The measure's backers announced Friday that Starr, a former federal judge and U.S. solicitor general, had signed on as their lead counsel and would argue the cases.
The new brief provides a preview of how Proposition 8's supporters plan to defend the measure. It asserts that the Supreme Court lacks the authority or historical precedent to throw out Proposition 8.
"For this court to rule otherwise would be to tear asunder a lavish body of jurisprudence," the court papers state. "That body of decisional law commands judges - as servants of the people - to bow to the will of those whom they serve - even if the substantive result of what people have wrought in constitution-amending is deemed unenlightened."
Starr declined comment Friday, but co-counsel Andrew Pugno said the brief was filed in response to a question the court's seven justices posed to lawyers on both sides, not as an attack on the gay married couples. "The people passed Prop. 8," he said. "We are defending that."
Pugno called Brown's decision to challenge the voter-approved measure, as well as the argument advanced by the attorney general, "totally unprecedented."
"His legal duty as attorney general of the state is to defend initiatives passed by the voters," he said. "Oftentimes, attorneys general have defended measures they personally opposed."
Jesse Choper, a constitutional law professor at the University of California, Berkeley Boalt School of Law, said Brown has to show that there is a right to marry or to be free from discrimination on the basis of sexual orientation that cannot be taken away by a constitutional amendment. "It is not an easy argument, but that doesn't mean it's not going to win," Choper said.
The cases are Strauss v. Horton, S168047; City and County of San Francisco v. Horton, S168078; and Tyler v. State of California, S168066.
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