San Francisco  - The California Supreme Court met Thursday in San Francisco to weigh a ban on same-sex marriage approved by voters last year.

The seven-member court is expected to decide within 90 days whether the ban known as Proposition 8 passed by voters in a November election is valid.

In the November 4 election, 52 per cent of voters favoured a ban on homosexual marriages be added to the state's Constitution by defining a married couple as only possible between a man and a woman.

The ballot measure followed an earlier ruling by the court in May that ruled an earlier ban on gay marriages that was in effect at the time was unconstitutional. That ban had been in place since 2000, when 62 per cent of California voters had restricted marriage to heterosexuals.

After the courts gave the green light to marriages of gays and lesbians, more than 18,000 homosexual couples got married in California before the November election.

San Francisco Attorney General Dennis Herrera called the issue a "fight for the equality of all citizens" and for the "protection of minority rights."

Groups against homosexual marriage, include religious organizations, and are being represented by lawyer Kenneth Starr, who is best known for the investigation that led to the impeachment of former president Bill Clinton. Starr argued that the decision of the voters is binding in this case.

More than 1,000 supporters of homosexual marriage demonstrated on the streets of San Francisco early Thursday.

"Taking away a civil right we had is a violent act," said activist Stuart Milk, nephew of slain gay activist Harvey Milk.

In the new hearings, the Supreme Court is also set to decide on the legality of the gay marriages conducted between the May court decision and the November vote. Since the November vote, same-sex marriages have been banned.

Right after their electoral defeat, supporters of homosexual marriage went into attack mode. Several couples, associations of homosexuals, the American Civil Liberties Union and municipal governments like those of San Francisco and Los Angeles have filed complaints before the Supreme Court.

Supporters of gay marriage say changing the constitution would violate the fundamental rights of lesbians and gays. They claim that such a drastic change should not be possible through a simple majority, and should instead require a two-thirds majority. dpa