California's highest court will give its ruling on the legality of the state's ban on gay marriages on Thursday, a long-awaited milestone that could have a nationwide impact on the issue.
A statement on the California Supreme Court website in San Francisco said the opinion would be made available by 10 am (1700 GMT) after hearing arguments for and against the ban at in March.
The court is addressing the constitutionality of a controversial amendment to the civil code which states that "only marriage between a man and a woman is valid or recognized in California."
The state already allows for civil unions between same-sex couples. Supporters of gay marriage stress that Proposition 22, adopted in a 2000 referendum, violates citizens' constitutional rights.
Denying same-sex couples marriage rights would paint California as "indifferent" to how gays are treated both inside and outside the state, warned San Francisco chief deputy city attorney Therese Stewart.
"If the state says that this is a marriage, it may be that some other states would not recognize it, but it would be sending the message that California considers its lesbian and gay couples equal."
In 2004, San Francisco mayor Gavin Newsom, citing California's guarantee of equal protection under law, began allowing same-sex marriages.
Several hundred gay couples were married at the city hall, but the procedures were subsequently invalidated. The case has now made its way to the state Supreme Court.
California Deputy Attorney General Christopher Krueger said "there is a rational basis for the state to adhere to the common and traditional definition of marriage" as affirmed by Proposition 22, and stressed that registered same-sex couples are provided with "all the rights and benefits associated with marriage."