But opponents say "Not so fast."
"This is a process that California had undertaken to try to protect marriage in their constitution before we even had a definition posed by the California Supreme Court" affirming the right of gays and lesbians to wed, Nimocks said. "Obviously, they care about it. It was a very free and democratic debate, and the decision of the sovereign people should ultimately be allowed to stand."
California has complicated history with gay marriage
The Supreme Court justices have discretion to rule narrowly or broadly on the twisting aspects of the legal and procedural questions raised.
Californians, it seems, cannot make up their minds about gay marriage, and the issue has been down a complicated legal road. For a one-month period in 2004, San Francisco unilaterally issued marriage licenses to same-sex couples, but that was halted by the state's highest court while the legal issues were sorted out.
California's Supreme Court then ruled in 2008 that same-sex marriages were legal. After the statewide ballot measure banning them passed with 52% of the vote later that year, gay and lesbian marriages were again put on hold. But a federal appeals court then found that measure unconstitutional.
"The U.S. Court of Appeals for the 9th Circuit, the intermediate appellate court, decided the case on a very narrow ground," said Amy Howe, an appellate attorney and editor of the widely read SCOTUSblog.com.
"They said we're not deciding whether there's some broad right to same-sex marriage. What we're deciding here is that, under the Supreme Court's own case law, if you have a right to same-sex marriage, which existed in California, and then the voters take it away out of animus towards gays and lesbians, that violates the Constitution. So the court could decide the case on that ground. It could also decide the case on the ground that is urged by the United States in the California case."
The Obama Justice Department took a separate position. Although the federal government is not a party in the Prop 8 case, it told the high court that if a state gives gays and lesbians all of the rights and responsibilities of a committed relationship, it should also give them that important label of marriage.
And there is an "out" if the court wants to avoid the issue entirely. Because the state's governor and attorney general refused to defend Prop 8 in court -- defying custom -- that left an important "standing" question: Could private citizens supporting the measure step in and make the case? If the justices decide they cannot, Prop 8 would be history, at least for now. But no binding precedent would be set for other states to follow on the constitutionality of same-sex marriage.
It's this generation's job to secure rights, plaintiff says
Some in the LGBT community worry things may be moving too soon, too fast; the country and courts may not be ready to embrace a constitutional right, and the cause of equality could be set back. A decade ago, no states allowed same-sex marriage, and public opinion was squarely against the idea.
But the Prop 8 plaintiffs say the time is right.
"Early on, Paul one day came home and he was a little upset, asking, 'Are we doing the right thing? People say we can set the movement back.' And I was in the kitchen and I actually raised my voice," Katami said, "and I actually don't raise my voice very often at him: 'I don't know where this is coming from! Do you want to be treated like a second-class citizen for the rest of your life?' Win or lose we can go to our graves saying that we tried, we did something."
"A lot of people have come before us and there's a responsibility that each generation has, especially within a minority community like the LGBT," Zarrillo said. "I think that our generation's responsibility is to win equality. And I think we are going to do that."