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. The decision came after several other states have legalized same-sex marriage in recent months. Backers of gay marriage in California had pledged to seek another ballot measure on the question of same-sex marriage in either 2010 or 2011.

The lawsuit the state Supreme Court ruled on was filed by same-sex couples and local governments who claimed that Proposition 8 became law in an illegal manner. The suit alleged the proposition was a revision -- not an amendment -- to the Constitution because it took away the fundamental rights of a group. A revision is considered a more significant change that requires more than a majority ballot vote.

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In California, after a March 5 hearing over Proposition 8, legal scholars and even many gay-marriage advocates said the state Supreme Court justices' questions signaled that a majority were unconvinced the amendment went too far. Justice Joyce Kennard, who voted to legalize gay marriage last year and whose vote is likely needed to overturn Proposition 8, peppered lawyers in favor of gay marriage with questions about why the court should overturn a voter-approved measure.