Opponents of same-sex marriage in California have appealed a U.S. federal judge's ruling overturning the state's ban on the unions.
Lawyers on Thursday filed an appeal to the U.S. Ninth Circuit Court of Appeals in San Francisco.
The appeal comes one day after U.S. District Court Judge Vaughn Walker struck down a state ban on same sex marriage, saying the measure than bans gay marriage fails to provide a rational basis for outlawing it.
Walker has scheduled a hearing for Friday.
Some legal experts believe the California case could lead to a U.S. Supreme Court ruling on whether it is constitutional to treat same-sex unions differently from those between a man and a woman.
In November of 2008, California voters narrowly approved a measure known as Proposition 8, which defines marriage as the union between a man and a woman.
The measure was approved just months after California's Supreme Court legalized same-sex marriages. Gay rights advocates said the ban violated the U.S. Constitution's provision on equal protection under the law.
In his 136-page decision, Judge Walker wrote that the ban prevents the state from fulfilling its constitutional obligation to provide marriages on an equal basis.
The court case, known as Perry vs. Schwarzenegger, was brought by two same-sex couples that were barred from marrying because of Proposition 8.
Gay marriage laws have been approved in five states, Connecticut, Iowa, Massachusetts, New Hampshire and Vermont, as well as the District of Columbia.
Some information for this report was provided by AP and Reuters.