(Corrects identification of Clinton spokesman in 21st paragraph of May 15 story.)

May 15 (Bloomberg) -- The California Supreme Court narrowly ruled that gay and lesbian couples have a constitutional right to marry, striking down laws barring same-sex nuptials and making the most populous state in the union the second after Massachusetts to legalize gay weddings.

Today's 4-3 ruling is a victory for gay rights groups and San Francisco, which in 2004 issued marriage licenses to almost 4,000 same-sex couples before being ordered to stop. The licenses were later voided. Supporters of the ban have said they would propose a state constitutional amendment barring the unions if the court struck down the ban.

The court went farther than any other, including the U.S. Supreme Court, in protecting the rights of gays and lesbians, said attorney Clifford Davidson, who filed a brief with the court opposing the ban. Sexual orientation is a ``suspect'' class, the California court wrote, meaning laws that impose different treatment on the basis of that characteristic should be viewed by judges with ``considerable skepticism.''

``The California constitution properly must be interpreted to guarantee this basic civil right to all Californians, whether gay or heterosexual, and to same-sex couples as well as to opposite-sex couples,'' the majority wrote.

The decision may reverberate in the U.S. presidential race in favor of presumptive Republican nominee Senator John McCain of Arizona, forcing candidates to explain their positions on same-sex unions, said Vikram Amar, a constitutional law professor at the University of California at Davis.

Feeds Perception

``It's hard to see how this will end up helping Democrats,'' Amar said before the ruling. ``It feeds into a kind of perception that this is what liberal activist judges do.''

Democratic presidential candidates Senator Hillary Clinton of New York and Senator Barack Obama of Illinois oppose same-sex marriage while supporting civil unions. McCain opposes gay marriage.

The majority said that, while historically marriage rights have belonged only to opposite sex couples, history isn't the only guide for determining constitutional rights.

The court pointed to its 1948 decision striking down state laws banning interracial marriage, echoing an argument made by supporters of gay marriage.

``An individual's sexual orientation, like race or gender, doesn't constitute a legitimate basis on which to deny or withhold legal rights,'' the court said. ``Same-sex couples should receive equal rights to marry and enjoy dignity equal to that of opposite-sex couples and not be treated as second class citizens.''

`Dignity and Respect'

Domestic partnerships deny same-sex couples the ``dignity and respect'' accorded to opposite-sex marriages, the court said.

The court directed state officials to guarantee that all local authorities comply with the ruling. The decision becomes final in 30 days unless extended by the court.

``The California Supreme court took a giant leap to ensuring justice for all people, regardless of sexual orientation, so we are very, very grateful,'' said San Francisco City Attorney Dennis Herrera.

Gay couples already enjoy many of the same legal rights as heterosexual couples under the state's domestic-partner law. The state has at least 92,000 same-sex couples, more than any other state, according to U.S. Census Bureau figures.

In 2000, 61 percent of California voters supported a ballot initiative defining marriage as between a man and woman. Any constitutional amendment banning gay marriage would be filed as a ballot item and subject to a referendum by California voters.

Schwarzenegger Opposes Amendment

``I respect the court's decision and as governor, I will uphold its ruling,'' said California Governor Arnold Schwarzenegger, a Republican, in a statement. ``As I have said in the past, I will not support an amendment to the constitution that would overturn this state supreme court ruling.''

Attempts to pass gay-marriage bills in the state legislature have previously failed after Schwarzenegger vetoed them.

The National Organization for Marriage California, a San Diego-based ballot-initiative committee, said it has collected 1.1 million signatures to put a proposition to amend the California constitution on the November ballot. It takes about 700,000 signatures to qualify for the ballot. State officials must first verify the gathered signatures before approving the amendment for the election.

The three presidential candidates reiterated their positions on the issue today in statements following the court ruling.

Candidates React

``McCain supports the right of the people of California to recognize marriage as a unique institution sanctioning the union between a man and a woman, just as he did in his home state of Arizona,'' McCain spokesman Tucker Bounds said. ``McCain doesn't believe judges should be making these decisions.''

Clinton campaign spokesman Mo Elleithee said his candidate believes there should be a federal law protecting civil unions, while marriage ``is an issue that should be left to the states.''

Jen Psaki, a spokeswoman for Obama, said the senator has ``always believed that same-sex couples should enjoy equal rights under the law,'' and ``that states should make their own decisions when it comes to the issue of marriage.''

National Attention

The lawsuits decided today were filed after San Francisco Mayor Gavin Newsom in 2004 ordered city officials to issue marriage licenses to same-sex couples in defiance of state laws that he said discriminated against homosexuals.

The move captured national attention as thousands of couples from 46 states and eight countries flocked to San Francisco City Hall, forming lines down the block to be wed. Massachusetts legalized gay marriage that year.

The mood at San Francisco City Hall today was jubilant with hundreds of people cheering the ruling.

``It's about human dignity, it's about civil rights --it's about time,'' Newsom told the crowd. ``By the way, as California goes, so goes the U.S.''

San Francisco's initiative galvanized opponents of same-sex marriage. President George W. Bush called for an amendment to the U.S. Constitution banning gay weddings and 11 states subsequently amended their constitutions to ban the unions.

Twenty-seven states have constitutional amendments banning gay weddings and 42 states have laws prohibiting the practice, according to the Pew Forum on Religion and Public Life.

Constitutional Amendment

``This ruling will unite the people of California and will propel their efforts to amend the state constitution,'' according to a statement by Liberty Counsel, a group opposing gay marriage that was a party to the litigation. ``Such an amendment is necessary to protect marriage from being undermined by the mere majority of four justices of the California Supreme Court.''

In March 2005, San Francisco Superior Court Judge Richard Kramer struck down California's law barring same-sex marriage as unconstitutional, saying the state can't prohibit people from choosing marital partners of the same sex just because it has always done so. That decision was overturned in a 2-1 ruling by a San Francisco appeals court in 2006.

California's domestic-partner law, which gives gay couples the same rights as heterosexual couples regarding financial support, property, child custody and taxes, doesn't go far enough in providing equal treatment to same-sex couples, they argued.

California argued the traditional view of marriage as being between a man and a woman was endorsed by voters in 2000, and that changing that policy should only be decided by voters or lawmakers.

``It is an unforgettable day for same-sex couples and advocates of equality across the nation,'' said Jennifer Pizer, senior counsel of Lambda Legal, a gay-rights group, in a statement. ``This ruling keeps a promise that every Californian should hold dear--the California constitution embraces everyone equally.''

The case is In re Marriage Cases, S147999, California Supreme Court (San Francisco.)

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

Last Updated: May 16, 2008 21:17 EDT