The California Supreme Court upheld a voter-approved ban on same-sex marriage Tuesday, but it also decided that the estimated 18,000 same-sex couples who tied the knot before the law took effect will stay wed.

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.

The court said the people have a right, through the ballot box, to change their Constitution.

“In a sense, petitioners’ and the attorney general’s complaint is that it is just too easy to amend the California Constitution through the initiative process. But it is not a proper function of this Court to curtail that process; we are constitutionally bound to uphold it,” the ruling said.

The announcement of the decision set off an outcry among a sea of demonstrators who had gathered in front of the San Francisco courthouse awaiting the ruling. Holding signs and waving rainbow flags, they chanted “Shame on you.” Many people also held hands in a chain around an intersection in an act of protest.

Gay rights activists immediately promised to resume their fight, saying they would go back to voters as early as next year in a bid to repeal Proposition 8.

The split decision provided some relief for the 18,000 same-sex couples who married in the brief time same-sex marriage was legal last year, but that wasn’t enough to dull the anger over the ruling that banned same-sex marriage.

“It’s not about whether we get to stay married. Our fight is far from over,” said Jeannie Rizzo, 62, who was one of the lead plaintiffs, along with her wife, Polly Cooper. “I have about 20 years left on this earth, and I’m going to continue to fight for equality every day.”

The state Supreme Court had ruled last May that it was unconstitutional to deny same-sex couples the right to wed. Many same-sex couples had rushed to get married before the November vote on Proposition 8, fearing it could be passed. When it was, gay rights activists went back to the court arguing that the ban had been improperly put to voters.

That was the issue justices decided today.

“After comparing this initiative measure to the many other constitutional changes that have been reviewed and evaluated in numerous prior decisions of this court, we conclude Proposition 8 constitutes a constitutional amendment rather than a constitutional revision,” the ruling said.

Today’s ruling of “no” and “yes” on same-sex marriage effectively left many people in the fight for equality with mixed emotions.

Locally, the San Diego LGBT Community Center expressed deep disappointment in the ruling from the California State Supreme Court, which failed to overturn Proposition 8. While the court did not invalidate the marriages performed for same-sex couples between June and November of last year, today’s ruling is a “major disappointment from a court that ruled for full equality just a year ago,” said Dr. Delores A. Jacobs, chief executive officer of The San Diego LGBT Community Center.

“It’s difficult to find joy in the fact that our state’s highest court didn’t forcibly ‘divorce’ the couples who were married last year,” Jacobs said. “There can be no doubt that our outrage would be considerably greater had those marriages been invalidated, but there is no cause for celebration. The bottom line is that justice and equality did not prevail today for anyone, and the Court has declared that Californians can simply vote to strip away even the most fundamental rights to equality enjoyed by their friends, family and neighbors.”

Those closest to the fight were angered.

“No civil rights movement has ever lost. Never. It is not a matter of if our community will win full equal rights, including marriage,” said Robin Tyler, a petitioner in the case to overturn Proposition 8. “It is only a matter of when. But as in all civil rights movements, we will have to fight like hell for it.”

While the ruling didn’t leave the community feeling victorious, it did provide solace because a component protects the 18,000 same-sex marriages performed during the six months when same-sex marriage was legal in California.

“While we are relieved that the High Court’s decision will not annul the marriages of the 18,000 committed couples who were legally wed between June and November of 2008, we are deeply saddened that others will not enjoy the same social and economic justice,” said Sara Beth Brooks, spokesperson for the San Diego Equality Campaign, one of seven civil rights organizations hosting this evening’s march and protest.

“Today, the State Supreme Court failed to perform one of its primary responsibilities, which is to protect minority groups from the whim of the majority. In November, a narrow majority of California voters stripped away marriage rights from same-sex couples,” Brooks said.