A federal judge overturned California's same-sex marriage ban Wednesday in a landmark case that could eventually land before the US Supreme Court to decide if gays have a constitutional right to marry in America.

Opponents of Proposition 8 cheer after hearing the decision in the United States District Court proceedings challenging Proposition 8 outside of the PhillipBurton Federal Building in San Francisco, Wednesday, Aug. 4, 2010. [Agencies]

Chief US District Judge Vaughn Walker made his ruling in a lawsuit filed by two gay couples who claimed the voter-approved ban violated their civil rights.

Gay couples waving rainbow and American flags outside the courthouse cheered, hugged and kissed as word of the ruling spread.

"This is a victory for the American people. It's a victory for our justice system," said former US Solicitor General Theodore Olson, who delivered the closing argument at trial for opponents of the ban.

He said the ruling "vindicates the rights of a minority of our citizens to be treated with decency and respect and equality in our system."

Despite the favorable ruling for same-sex couples, gay marriage will not be allowed to resume immediately. Judge Walker said he wants to decide whether his order should be suspended while the proponents of the ban pursue their appeal in the 9th US Circuit Court of Appeals.

The judge ordered both sides to submit written arguments by Aug. 6 on the issue.

Supporters argued the ban was necessary to safeguard the traditional understanding of marriage and to encourage responsible childbearing.

California voters passed the ban as Proposition 8 in November 2008, five months after the state Supreme Court legalized gay marriage.

Walker, however, found that the gay marriage ban violates the Constitution's due process and equal protection clauses while failing "to advance any rational basis in singling out gay men and lesbians for denial of a marriage license."

"Indeed, the evidence shows Proposition 8 does nothing more than enshrine in the California Constitution the notion that opposite-sex couples are superior to same-sex couples," the judge wrote in his 136-page ruling.

Both sides previously said an appeal was certain if Walker did not rule in their favor. The case would go first to the 9th US Circuit Court of Appeals, then the Supreme Court if the high court justices agree to review it.

Walker heard 13 days of testimony and arguments since January during the first trial in federal court to examine if states can prohibit gays from getting married.

The ruling puts Walker at the forefront of the gay marriage debate. The longtime federal judge was appointed by President Ronald Reagan.

The verdict was the second in a federal gay marriage case to come down in recent weeks. A federal judge in Massachusetts decided last month the state's legally married gay couples had been wrongly denied the federal financial benefits of marriage because of a law preventing the US government from recognizing same-sex unions.

The plaintiffs in the California case presented 18 witnesses. Academic experts testified about topics ranging from the fitness of gay parents and religious views on homosexuality to the historical meaning of marriage and the political influence of the gay rights movement.

During trial, Olson told Judge Walker that tradition or fears of harm to heterosexual unions were legally insufficient grounds to discriminate against gay couples.

Olson teamed up with David Boies to argue the case, bringing together the two litigators best known for representing George W. Bush and Al Gore in the disputed 2000 election.

Defense lawyers called just two witnesses, claiming they did not need to present expert testimony because US Supreme Court precedent was on their side. The attorneys also said gay marriage was an experiment with unknown social consequences that should be left to voters to accept or reject.

Former US Justice Department lawyer Charles Cooper, who represented the religious and conservative groups that sponsored the ban, said cultures around the world, previous courts and Congress all accepted the "common sense belief that children do best when they are raised by their own mother and father."

In an unusual move, the original defendants, California Attorney General Jerry Brown and Gov. Arnold Schwarzenegger, refused to support Proposition 8 in court.

That left the work of defending the law to Protect Marriage, the group that successfully sponsored the ballot measure that passed with 52 percent of the vote after the most expensive political campaign on a social issue in US history.

Currently, same-sex couples can only legally wed in Massachusetts, Iowa, Connecticut, Vermont, New Hampshire and Washington, D.C.