May 26 (Bloomberg) -- The California Supreme Court upheld Proposition 8, the ballot initiative passed in November that outlawed same-sex weddings, a practice that’s now legal in Iowa and three other states.

The court ruled that 18,000 gay marriages performed before the ban remain valid. Gay rights advocates said they may ask voters next year to overturn Proposition 8, claiming opposition to gay marriage is waning. Fifty-two percent of voters supported the initiative, which amended the state constitution to recognize only marriages between a man and a woman. Sixty-one percent of voters supported a similar measure in 2000.

The California high court legalized gay weddings a year ago, ruling 4-3 that state laws against the practice were unconstitutional. The court ruled 6 to 1 today in favor of upholding Proposition 8, saying it was ruling only on the ability of voters to pass a ballot measure rather than whether gay marriage should be legal.

“The principal issue before us concerns the scope of the right of the people, under the provisions of the California constitution, to change or alter the state constitution itself through the initiative process,” the court wrote, “not to determine whether the provision at issue is wise or sound.”

The November ban sparked protests across California and led activists to create Web sites that identified individuals who donated money to support the measure and boycott donors’ business. The 14-word ballot measure overrode the court’s May 15, 2008, ruling, which at the time made California the second U.S. state after Massachusetts to legalize gay weddings.

Schwarzenegger’s Prediction

“I believe that one day either the people or courts will recognize gay marriage,” California Governor Arnold Schwarzenegger said in a statement. “Regarding the 18,000 marriages that took place prior to Proposition 8’s passage, the court made the right decision in keeping them intact.”

Supporters of gay marriage gathered at an emotional news conference at San Francisco City Hall, where hundreds of gay couples flocked in 2004 when the city issued marriage licenses before being halted by a court. Proposition 8 could be overturned by ballot measure next year, they said.

“It is clear this is not the end,” said San Francisco Deputy City Attorney Therese Stewart, her voice trembling. “We have already seen a sea change in public opinion about the rights of gay couples.”

Since Proposition 8 passed, Iowa, Vermont and Connecticut have legalized gay weddings. Maine lawmakers approved a gay marriage bill on May 5 that was signed by the governor and hasn’t taken effect. Massachusetts legalized the marriages in 2004.

700,000 Signatures

Almost 700,000 signatures must be gathered in California by Sept. 25 to put an initiative to amend the state constitution on the June 2010 ballot.

Proposition 8 doesn’t alter or affect the California Supreme Court’s 2008 ruling that same-sex couples have a constitutional right to establish “an officially recognized family relationship,” according to today’s ruling. The proposition added the sentence, “Only marriage between a man and a woman is valid or recognized in California,” to the constitution.

The measure doesn’t change gay couples’ legal rights, only their ability to have their partnerships designated as marriages, the court said. Proposition 8 wasn’t a revision to the constitution that would require approval from lawmakers, as opponents argued, because it didn’t change the way government operates, the court said.

California’s domestic partner law gives gay couples the same rights as heterosexual couples regarding financial support, property, child custody and taxes.

‘Escalate’ tactics

“We believe it’s time to escalate the tactics in this movement,” said Joe Capley-Alfano, who wed his partner before Proposition 8 was passed. “We don’t have the luxury of time to wait any longer.”

Capley-Alfano says he lacks health insurance because his employer doesn’t offer it and his partner’s union-provided health care program isn’t offered to him because the union doesn’t recognize the couple’s marriage or domestic partnership.

Supporters of Proposition 8 said they were pleased by the court’s decision.

Years of Campaigning

“This is a great day for traditional marriage and the family,” said Mathew Staver, an attorney who represented anti gay-marriage groups in court, in an e-mailed statement. “Political leaders who say that we should give up the battle on traditional marriage are out of touch with the American people,”

Efforts to repeal Proposition 8 would be “vigorously contested,” Andrew Pugno, another attorney for groups supporting the measure, said in the statement.

“I’m happy that Prop 8 was upheld,” said Jana Kulinich, 19, a student at American River College in Sacramento, who stood outside the courthouse today. “Marriage by nature is between a man and a woman.”

Gay couples and the city of San Francisco, which briefly allowed gays to marry in 2004, sued to overturn the ballot initiative. They argued that it changed a fundamental civil right of a protected minority and amounted to a revision, not an amendment, to the constitution.

Revising the California constitution requires a two-thirds majority vote by the legislature before asking voters to weigh in, they argued in court papers.

Amendment, Not Revision

Proposition 8 supporters countered that the measure didn’t revise the constitution because it didn’t change the way the state government operates. The court can’t overturn the will of voters, even if they made an unwise decision on individual rights, the measure’s supporters argued in court papers.

A federal lawsuit filed May 22 in San Francisco seeks to overturn Proposition 8. The lawsuit, on behalf of two gay couples wishing to marry, was filed by Theodore Olson, the former U.S. solicitor general who represented former President George Bush during the 2000 U.S. Supreme Court case that decided the presidential election, and by David Boies, who represented former Vice President Al Gore in the same case.

California has at least 92,000 same-sex couples, according to the U.S. Census Bureau, more than any other state.

“What do we want? Equality. When do we want it? Now,” several hundred protesters opposing the ban chanted outside the state Supreme Court in San Francisco before the decision was announced. They switched their chant to “shame on you,” upon learning of the ruling.

‘Shell-Shocked’

“Honestly, I feel shell-shocked,” said Lindasusan Ulrich, 40, who married her partner before Proposition 8 was passed and wore her wedding dress in front of the courthouse today. “It’s really dehumanizing to have people vote on whether or not I’m a full citizen.”

The cases are Karen Straus v. Mark Horton, S168047; Robin Tyler v. California, S168066; and San Francisco v. Mark Horton, S168078, California Supreme Court (San Francisco).

To contact the reporter on this story: Karen Gullo in the California Supreme Court in San Francisco at kgullo@bloomberg.net.

Last Updated: May 26, 2009 21:15 EDT