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California's highest court heard arguments Tuesday by same-sex marriage supporters and opponents who agreed on marriage's social significance, but diverged sharply over whether withholding the institution from gay couples violates their civil rights.

The state Supreme Court spent more than three hours listening to arguments that depriving gay men and lesbians of the marriage title counts as discrimination — even in a state that grants them the same rights as married couples.

"Substantial equality is not equality. Substantial progress is not progress," said Chief Deputy City Attorney Therese Stewart, who represented the city in a lawsuit supporting gay marriage rights.

"The name 'marriage' matters," Stewart added. "It communicates something all people can understand. It communicates loyalty and intimacy and commitment."

Attorneys for the state, Governor Arnold Schwarzenegger and two groups opposed to gay marriage argued that domestic partnership laws enacted by the California Legislature go far enough in ensuring equal treatment for same-sex couples.

"When the state is acting so aggressively to protect the lives and protect the rights of domestic partners, it's not irrational to protect a definition of marriage that has stood the test of time," said Deputy Attorney General Christopher Krueger.

San Francisco, two gay rights groups and 23 couples sued to overturn California's marriage laws four years ago after the court halted a wedding spree at San Francisco City Hall. More than 4,000 same-sex couples exchanged vows at the direction of Mayor Gavin Newsom months before gay marriage became legal in Massachusetts, although the high court ultimately voided the unions.

The seven justices, jointly hearing six separate lawsuits Tuesday, asked repeatedly whether marriage was a civil right recognized under the state Constitution and if a ruling by their predecessors on the bench 60 years ago legalizing interracial marriages gave them a precedent for striking down the state's same-sex marriage ban.

"There was a very long tradition of treating a wife as the property of her husband. There was a long tradition of not allowing women to vote," observed Associate Justice Joyce Kennard.

Shannon Minter, a lawyer from the National Center for Lesbian Rights who was representing 15 Bay Area same-sex couples before the court, said sexual orientation — like gender and race — has no bearing on a person's ability to form lasting, loving relationships.

"The fact that discrimination has been going on for a long period of time is really a misuse of the word 'tradition,"' Minter said. "People want to marry the one person who, to them, is irreplaceable. We demean ourselves as a society if we don't give individuals the freedom to marry and to choose whom to marry."

From their questions, the justices seemed concerned with how to reconcile the constitutional arguments with a voter-approved measure that strengthened California's one-man, one-woman marriage law eight years ago.

Glen Lavy, an Alliance Defense Fund lawyer representing the sponsors of Proposition 22, told the court it would be circumventing the democratic process if it struck down the law, a point debated by the justices.

"Isn't the ultimate expression of the people's will: the Constitution, both federal and state?" asked Chief Justice Ron George.

"Does that lead this court to no role? What is our role?" asked Associate Justice Kathryn Werdegar.

"So the court was wrong when it invalidated the anti-miscegenation laws?" George said.

Lavy said drawing parallels between bans on interracial and same-sex marriage was inappropriate because allowing marriage between people of different races "did not redefine what marriage is." Allowing partners in a same-sex relationship to wed would, according to Lavy.

"Marriage is not what they want because the law does not say gay men and lesbians can't get married," he said. "They are not allowed to form a same-sex couple and call it a marriage."

A trial court judge in San Francisco agreed with gay rights advocates and voided the state's marriage laws in April 2005. A midlevel appeals court overturned his decision in October 2006.

Since the California cases were filed, the top courts in six other states have been asked to legalize same-sex marriage. New Jersey's top court gave lawmakers the option of adopting civil unions as an alternative and a ruling is pending in Connecticut, but none of the other courts was persuaded.

In front of the building where Tuesday's hearing in California took place, some groups protested from the sidewalk, holding signs reading "Re-criminalize sodomy" and "Gay

pervert."

Counter protesters held signs reading "Stop ignorance. Being gay is not a choice" and "Your religion is not my government."

Following the hearing, lawyers on opposite sides of the issue said it was impossible to predict the outcome from the questions the justices asked.

"They are clearly divided. I'm just not sure which side is in the majority," Krueger said. "They weren't giving anyone a free pass today."

Geoffrey Kors, executive director of the gay rights group Equality California, agreed.

"All seven of them asked the appropriate questions to get the attorneys to what is at the heart of these cases — from what Proposition 22 means to 'Are domestic partnerships equal enough?'," Kors said.

The court has 90 days in which to issue its decision.

Gay marriage opponents suggested that if they are on the losing side, it would give momentum to a campaign already under way to amend the state Constitution to prohibit same-sex unions and possibly rescind domestic partner rights.