This post has been updated with additional information.

Gay-marriage advocates were celebrating Wednesday's Supreme Court decisions not just because of what they mean today -- making gay marriage legal in California and federal benefits available to married gay couples -- but what they could mean tomorrow.

As Andrew Cohen explains, the Court didn't take a position on the merits of the arguments for and against California's Proposition 8. But at the same time, it struck down the Defense of Marriage Act on broad constitutional grounds. Advocates believe that gives them an opening to challenge marriage bans in the 31 states where they're currently on the books. If they're right and the bans start to fall, gay marriage could quickly be legal across the nation.

"The principles the court articulated today mean we are going to have marriage equality in all 50 states," said David Boies, one of the lawyers on the winning side of the Prop 8 case. In the DOMA case, he said, the court "held that there was no rational basis, no legitimate justification, for discrimination against gay and lesbian citizens; that that kind of discrimination seriously harms us; and that there is no justification other than malice and disapproval" for it. Boies spoke to reporters on a conference call organized by the American Foundation for Equal Rights.