San Francisco ? A state appeals court upheld California’s ban on gay marriage Thursday, a critical defeat for a movement hungry for a win after similar losses in two other states.

In reversing the March 2005 ruling of a San Francisco trial judge, the 1st District Court of Appeal agreed with the state’s attorney general, who argued it is up to the Legislature, not the courts, to change the traditional definition of marriage as a union between a man and a woman.

“We conclude California’s historical definition of marriage does not deprive individuals of a vested fundamental right or discriminate against a suspect class,” the court said in a 2-1 decision. “The time may come when California chooses to expand the definition of marriage to encompass same-sex unions. That change must come from democratic processes, however, not by judicial fiat.”

The justices, in their 128-page opinion, noted that California’s ban on same-sex marriage does not discriminate against gays and lesbians because of the state’s strong domestic partner law, which gives registered couples most of the same rights as married spouses in California.