“Our love is the same, our needs, it's all the same, and I think the idea that we're somehow so different, it's so important for people to understand, we're not,” Forney said.

At the recent Los Angeles rally, supporters of same-sex marriage said they are optimistic. Alejandro Escoto and his partner Ramiro Vasquez hope a favorable ruling will allow them to get married.

“Because we have a life together for 15 years, and for the state or for someone to tell us that's not right, that's not OK,” Vasquez said.

Nine U.S. states and the District of Columbia permit gay marriage. Thirty-nine others states ban it. The court could rule narrowly on the California law, or more broadly on the issue nationwide.