A federal judge overturned California's ban on same sex marriage, saying that the voter-approved restriction violated the highest law of the land, the US constitution.
The ruling on Wednesday by Judge Vaughn Walker overturned a 2009 ruling by the California Supreme Court that upheld a state-wide ballot proposition in 2008 that reserved marriage for two people of the opposite sex.
The judge ordered an injunction against enforcement of the Proposition 8 ballot item but issued a temporary stay until he decides whether to suspend his ruling while it is being appealed.
The stay means that same-sex couples are still prohibited from marrying.
Opponents of gay marriage pledged to appeal on Wednesday's ruling and the case is considered likely to end up in the US Supreme Court. "In America, we should respect and uphold the right of a free people to make policy choices through the democratic process," Mr Brian Raum, who was part of the legal team defending Proposition 8, told reporters.
Judge Walker ruled that the ballot measure "prevents California from fulfilling its constitutional obligation to provide marriages on an equal basis".
"Proposition 8 fails to advance any rational basis in singling out gay men and lesbians for denial of a marriage license," Walker wrote in a 136-page ruling.
The constitutional right to marry, Walker said, "protects an individual's choice of marital partner regardless of gender". Walker added that domestic partnerships in California, available to same-sex couples, are a "substitute and inferior institution" that lack the social meaning and cultural status of marriage.
He also observed that children who grow up in same-sex marriages are as well adjusted as those from heterosexual relationships.
California Governor Arnold Schwarzenegger welcomed the judge's decision. "For the hundreds of thousands of Californians in gay and lesbian households who are managing their day-to-day lives, this decision affirms the full legal protections and safeguards I believe everyone deserves," he said in a statement.
The gay marriage issue has been unsettled for years in California, where the top California state court had given the green light to same sex marriage in May 2008, only to have 52 percent of the voters in November 2008 ban the practice following a massive campaign by church organisations.
The ban was then upheld in May 2009 by the California Supreme Court, which however did recognize the 18,000 gay marriages that were licensed by the state between May and November 2008.