By Peter Bowes
BBC News, Los Angeles
The decision by California's Supreme Court to uphold a ban on same-sex marriage has been met with anger and disappointment by gay rights campaigners.
Campaigners hope to force another state-wide vote on gay marriage
The ruling means homosexual couples in America's most populous state will continue to be barred from tying the knot.
A crowd of protesters outside the San Francisco courthouse chanted "Shame on you, shame on you," as the decision was announced.
"It is a real blow and it's a real travesty of justice that a majority of voters can take away the rights on a minority," says Marc Solomon from the gay rights group, Equality California.
'Sweet and sour'
The court refused to overturn Proposition 8, a ballot measure defining marriage as being between a man and a woman.
The amendment to the state's constitution passed last November, with a 52% majority.
But the justices also decided that the estimated 18,000 same-sex couples that wed before the law took effect would remain married.
"I am very, very disappointed," said Eric Monriquis, who married his partner last year.
"It's a sweet and sour thing. We're still married but we are members of a very small minority, 18,000 people. It's sad."
Rabbi Denise Eger added: "This is nothing short of apartheid in our own state, that some people were allowed to be married and others will never have that right."
Conventional marriage campaigners welcomed the court's decision.
"This is a victory for the people," said Lou Sheldon of the Traditional Values Coalition.
"I am thrilled that the court saw the light of day."
California Governor Arnold Schwarzenegger said he would uphold the court's decision.
But, he added: "I believe that one day either the people or courts will recognize gay marriage."
Gay rights organisations have pledged to continue their fight to get same-sex unions recognised as marriages in California.
"We are re-grouping," explains Mr Solomon.
"We are ready to win marriage back. We know the path is steep and we know that we can do it. Justice will prevail," he added.
Equality California has already deployed field workers to areas of California where there was a strong vote in favour of Proposition 8.
The process of getting the gay marriage issue back on the ballot paper involves collecting almost a million signatures.
The group has said its supporters want to give California voters a chance to reconsider the matter in the November 2010 election.
In the meantime, same-sex couples in California will continue to have the option of entering a domestic partnership agreement, although activists say it is no match for marriage.
"Marriage is commitment, marriage is responsibility for one another, marriage is what government and our society give as a sign of respect for a relationship," explains Mr Solomon.
"An institution that was created because people didn't want to give marriage is simply not acceptable. We won't settle until our community is treated as full equals."
Gay rights groups have said they intend to stage further protests on the streets of major cities around California. Governor Schwarzenegger urged them to respond "peacefully and lawfully".