NEW YORK - The California Supreme Court upheld a ban on same-sex marriage Tuesday, dealing a blow to advocates of gay marriage. With Jewish groups on either side of the blistering dispute, the court also ruled that the 18,000 gay couples who wed before November, when the ban took effect, would remain married. Within minutes of the ruling, advocates of gay marriage pledged to renew their fight against Proposition 8, the ballot measure that banned same-sex marriage. In November, California voters passed Proposition 8 by a 52 to 48 margin, reinstating a ban on same-sex marriage months after the state Supreme Court approved gay marriage in a landmark ruling in May. "This isn't a surprise, but it is a big disappointment," Rabbi Lisa Edwards of Beth Chayim Chadashim, Los Angeles' oldest gay and lesbian synagogue, said yesterday just after the court handed down its 6-1 decision. "This is a civil rights issue, not a religious issue," said Edwards, who married her partner in a religious ceremony in 1985, and was married in a civil ceremony in July 2008. "In the end, I think we'll be successful, but we're so sad for this setback." Advocates of same-sex marriage, who said the decision failed to uphold equal protection, also pledged to renew their fight against Proposition 8. "We are planning, and have been planning, to move forward to challenge this outcome," said Douglas Mirell, president of the Progressive Jewish Alliance. Mirell said the ruling created three unequal classes of citizens: heterosexual couples who can marry at will, gay couples who face the November ban on gay marriage; and gay couples who were fortuitous in marrying before the ban took effect. "It is wholly illogical to create a system by which your rights are dependent upon the happenstance of timing," he said. To be sure, the ballot measure this past fall divided California Jews, who in the end opposed Proposition 8. According to exit polls at the time, Los Angeles Jews voted overwhelmingly against the amendment to ban same-sex marriage, with 78 percent voting against the ban and only 8% supporting it. Nationwide, the issue galvanized Jewish organizations both in support - and in opposition - of same-sex marriage. On Tuesday, the Union of Orthodox Jewish Congregations of America, which supported Proposition 8, reiterated its opposition to same-sex marriage. "We supported Proposition 8 because in addition to our religious values, which we do not seek to impose on others, we fear that same-sex marriage poses a grave threat to the fundamental civil right of religious freedom," the OU said in a statement. Howard Beigelman, the group's deputy director of public policy, cited several such cases, including a New Jersey church that was sued after it refused to rent its facility for a gay marriage. Vermont and Connecticut, which have gay marriage laws on the books, have strong exemptions for religious institutions, he noted. "From our perspective, if a synagogue or a school or an institution wants to do something, that's their prerogative. We're not going to throw them out of the OU. But if they don't want to, they shouldn't be sued," he said. On Tuesday, California Jews who have opposed Proposition 8 were planning rallies to reinvigorate their fight. "At this point, it's a lot of effort to comfort one another and to reenergize ourselves for the next step," said Sandy Bredt, executive director of Kehilla Community Synagogue in Piedmont, Calif. Last spring, Kehilla staged a group marriage ceremony for seven same-sex couples in response to the community's opposition to Proposition 8. Speaking Tuesday morning before the ruling, Bredt stressed that the couples married at Kehilla would still be married after the court's decision. "They're married now. They'll be married at five after 10 [o'clock] when the ruling is handed down," she said. "They are family, and the voters don't get to decide about that. Period."