California judge overturns ban on homosexual marriages

But US district court chief judge Vaughn Walker ordered the voter-approved ban, known as Proposition 8, to remain in place at least temporarily until he decides a request by supporters of the ban to keep it intact while the case moves to a higher court.

Although the result leaves homosexual couples unable to marry for now, Walker said Prop 8 opponents "demonstrated by overwhelming evidence" that it violates due process and equal-protection rights under the US Constitution.

"Proposition 8 fails to advance any rational basis in singling out gay men and lesbians for denial of a marriage licence," Walker wrote in the conclusion of the 136-page opinion.

Outside the federal courthouse in San Francisco, a cheer went up among a group of about 70 supporters of same-sex marriages carrying small US flags, as a large rainbow-striped flag — the symbol of the homosexual rights movement — waved overhead.

California governor Arnold Schwarzenegger, who has said he personally supports homosexual marriages but would abide by the will of voters and the courts, said the decision "affirms the full protections and safeguards I believe everyone deserves".

The highly anticipated ruling marks a major turning point in a social debate that has sharply divided the American public and its political establishment.

Advocates of homosexual rights and civil libertarians have cast the legal battle as a fight for equal rights, while opponents, including many religious conservatives, see same-sex marriage as a threat to the traditional family.

Both sides have said an appeal to the 9th US circuit court of appeals was certain regardless of the outcome on Wednesday. The case could then go to the Supreme Court, provided the high court's justices opt to hear it.

"I'm thrilled," homosexual marriage proponent Steven Ray Davis said at the courthouse. "[But] we still have a long way to go."

The case against California's Prop 8, a constitutional amendment approved by voters in November 2008 defining marriage as a relationship between a man and a woman, marks the first challenge in a federal court to a state law barring same-sex matrimony.

Thirty-nine US states have laws explicitly prohibiting homosexual marriage — 30 adopted in their constitutions. Five states and the district of Columbia recognise homosexual marriage — Iowa, Connecticut, New Hampshire, Vermont and Massachusetts.

Early last month, a federal judge in Massachusetts ruled that a 1996 federal law, the Defence of Marriage Act, or DOMA, which denies federal recognition of same-sex marriages, even in states where it is allowed, was unconstitutional.

The federal government has 60 days to decide whether to appeal against that ruling.

The two lead attorneys in the California case are Ted Olson and David Boies, who opposed each other in the landmark Supreme Court case that decided the outcome of the disputed 2000 US presidential election and put George W Bush in the White House.

Some advocates of homosexual rights were initially hesitant to bring a federal challenge to Prop 8, fearing an eventual defeat before the conservative-leaning US Supreme Court.