The California Supreme Court has upheld the validity of Proposition 8, the state's controversial gay marriage ban. But justices agreed to uphold the legality of 18,000 gay and lesbian marriages performed during the “summer of love.”

Tuesday's split decision was widely expected by supporters on both sides of the issue.

Proposition 8 placed a gay marriage ban in the California Constitution, effectively overturning the high court's 4 to 3 decision that legalized gay marriage nearly a year ago.

Gay rights activists argued that the measure was an illegal revision to the state constitution. They claimed the measure fundamentally altered he document – by taking away previously granted rights protected by the constitution – and was not an amendment at all.

Activists have said a split decision would not be acceptable and plan to protest the decision.