The California Supreme Court in one of the most anticipated court decision upheld a voter-approved ban on same-sex marriage Tuesday.

Marriages of approximately 18,000 couples prior to the prior to the passage of proposition 8 last November remained valid.

Gay rights activists plan to repeal the ban and turn back to voters next year. As the decision was announced, gay rights advocates on the courthouse steps in San Francisco began shouting Shame on you”.

The 6-1 decision written by Chief Justice Ron George rejected an argument by gay rights activists that the ban revised the California Constitution's equal protection clause to such a dramatic degree that it first needed the Legislature's approval.

Only marriage between a man and a woman is valid or recognized in California, Chief Justice Ronald George wrote in the court's opinion.

Outside the court's offices, several same-sex couples who had wed in recent months vowed they would commit acts of civil disobedience in response to the ruling.

Prop 8 was passed last November with a 52 percent majority.

California Ban