Gay marriage advocates on Thursday will ask the California Supreme Court to overturn a second voter-approved same-sex marriage ban, in a cultural battle that has divided the United States.

Social conservatives and liberals both consider California a trend-setter that can shape the same-sex marriage agenda, even though an overwhelming majority of U.S. states have laws stopping gay couples from wedding.

The same court last year overturned a voter-approved law banning gay marriage, opening the way to gay couples wedding in the most populous state. Some 18,000 couples married.

But voters in November passed a constitutional amendment, Proposition 8, limiting marriage to a man and a woman, which sparked national protests -- and a new court fight.

Only a handful of countries, mostly European nations, allow gay marriage.

Gay marriage opponents said overturning the California ban would change the nature of state government by gutting the people's right to make law.

The court would create "a sweeping power vested in the least-democratic branch that overrides the precious right of the people to determine how they will be governed," same-sex marriage opponents said.

Gay marriage proponents, led by former governor and current California Attorney General Jerry Brown, argue that the right to marry is part of the "inalienable right" to liberty, so the state Supreme Court must strike down even an amendment to the constitution limiting it.

Minority groups fearing the amendment could become a blueprint for institutionalized discrimination and conservative religious groups who see marriage between a man and a woman as "traditional" have turned the legal fight into a broad cultural question.

The court will hear three hours of arguments on Thursday and then have 90 days to issue an opinion.