California's battle over same-sex marriage went before the state's highest court, with civil rights lawyers seeking to overturn a voter-approved ban on gay weddings.
Hundreds of supporters and opponents gathered outside the Supreme Court in San Francisco for the hearing, which came 10 months after the court legalized gay marriage in a landmark ruling last May.
That ruling was cast into doubt last November when voters passed a change to California's constitution that redefined marriage in the state as a union between a man and a woman.
Supporters of same-sex marriage are seeking to have the results of the referendum, known as Proposition 8, quashed on the grounds that minority rights should not be vulnerable to a simple majority vote.
Appearing Thursday before the seven California Supreme Court justices who will rule on the case within 90 days, rights lawyers urged the court to strike down Proposition 8 as discriminatory.
"Prop. 8 changes the basic nature of our government from one in which the majority protects the rights of minorities," said Shannon Minter, lead counsel for those seeking to overturn the measure.
"It takes away the right to be treated with equal dignity and respect ... A simple majority cannot be allowed to take any rights away from a historically protected minority."
But justices strongly indicated they were leaning toward rejecting the requests to invalidate Proposition 8.
Justice Joyce Kennard, who voted with the majority in last year's 4-3 ruling that legalized gay marriage, repeatedly made it clear she disagreed that Proposition 8 was an illegal revision of the state Constitution.
Instead, she focused on voters' approval of the proposition, saying the court could not "willy-nilly disregard the will of the people to change the state constitution as they have in the past."
Kennard referred to a similar situation in a case involving the death penalty, when the California Supreme Court ruled it was unconstitutional. Voters later passed an amendment reinstating the death penalty, and the state Supreme Court refused to overturn the amendment.
Opponents of gay marriage meanwhile defended the right of voters to amend the state constitution.
Their case was argued by Kenneth Starr, best known as the independent counsel who pursued former President President Bill Clinton during the Monica Lewinsky scandal.
"The right of the people is inalienable to change their constitution through the amendment process," said Starr. "The people are sovereign and they can do very unwise things."
Last November's referendum result came as a stinging blow to same-sex couples who six months earlier had celebrated after the Supreme Court voted in favor of overturning a previous ban on gay weddings in the state.
That historic decision prompted around 18,000 same-sex couples to exchange vows as California became only the second US state to allow gay marriage.
However, the issue was forced back on the agenda later by social conservative and religious groups, which successfully gathered enough support for Proposition 8 to be placed on ballots at November 4 polls.
When the measure was approved by a margin of 52.5 to 47.5 percent, the status of same-sex marriages was cast into doubt.
Justices appeared to be opposed to retroactively invalidating gay marriages performed last year before Proposition 8 was approved.
Before Thursday's hearing got underway, anti-gay marriage protestors outside brandished banners reading "Homo Sex is Sin," "Gay = Pervert" and "The Wages of Sin is Death."
Other signs read "Yes on 8," and "A moral right cannot be a civil right."
A woman used a bullhorn to scream at same-sex marriage supporters, who responded by singing and playing guitars.