But Chief Deputy San Francisco City Attorney Therese Stewart and National Center for Lesbian Rights Legal Director Shannon Minter said they think litigation in California may be close to an end.
"It's hard to predict whether they'll continue to fight," said Stewart, referring to gay marriage opponents, "but we're not terribly anxious about it."
Elsewhere, however, Minter said, "there are cases all over the country" challenging state bans on same-sex marriage.
The two attorneys spoke at a panel during the ABA's annual meeting, which continues in the city through Tuesday.
The session was entitled "More Than an Equal Sign: the Defense of Marriage Act, Proposition 8, the Supreme Court and Your Practice."
In one of its two rulings on June 26, the U.S. Supreme Court ruled that the sponsors of Proposition 8, California's voter-approved ban on same-sex marriage, had no standing to appeal a lower court ruling striking down the ban.
That decision left in place a federal trial court judge's injunction blocking enforcement of Proposition 8, and gay and lesbian weddings resumed in California two days later.
In the second ruling, made in the case of New York widow Edith Windsor, the court struck down a key provision of the federal DOMA law that barred the U.S. government from giving federal benefits and tax advantages to legally married gay and lesbian couples.
The court did not rule directly in either case on whether a state prohibition on same-sex marriage violates the U.S. Constitution.
But Minter said the Windsor decision's reliance on constitutional equal protection and due process doctrines appears to provide a foundation for state law challenges.
"There's almost nothing in the Windsor decision that wouldn't apply to state marriage laws," he told the audience.
Thirteen states and the District of Columbia now allow same-sex marriages.
States where lawsuits contesting gay marriage bans are pending include Hawaii, Nevada, Utah, Pennsylvania, North Carolina, Virginia and New Mexico, among others.
The Hawaii and Nevada cases are now on appeal before the 9th U.S. Circuit of Appeals in San Francisco and are being considered together, Minter said.
In those two cases, federal trial judges upheld a Hawaii law and Nevada state constitutional amendment limiting marriage to opposite-sex couples.
The 9th Circuit put the two cases on hold until the Supreme Court ruled on Proposition 8 and DOMA, and has now resumed receiving briefs in the two appeals. A hearing has not yet been scheduled.
Minter said that another type of litigation pending in a number of states is lawsuits seeking recognition of marriages of couples who were legally wed in one state but moved to another state.
"I think people are saying, 'We're not going to sit back any more,'" Minter said.
Stewart said litigation in California appears to be nearing an end after the Proposition 8 sponsors and San Diego County Clerk Ernest Dronenburg lost bids to the California Supreme Court for an immediate stay that would have reinstated Proposition 8.
The Proposition 8 backers still have a petition pending before the state court seeking review of their claim that the federal injunction protects only two couples who sued for the right to marry.
Stewart, who represented the city in the federal Proposition 8 case, predicted, "It's very likely we will see a denial of the petition very soon."
Dronenburg withdrew a similar petition on Monday.
Earlier, the Proposition 8 sponsors asked U.S. Supreme Court Justice Anthony Kennedy for an emergency stay on June 29, and were turned down by Kennedy without comment the next day.
Stewart and Minter noted that in the two rulings in June, the U.S. Supreme Court followed a judicial tradition of avoiding a broad decision in situations in which a case can be resolved on narrow grounds.
But both forecast that the court will eventually rule on state marriage laws and that a majority of the justices will find the bans unconstitutional.
"They may postpone it as long as they can, but I do think that at the end of the day we'll get there in the Supreme Court," Stewart predicted.