The Supreme Court's decisions Wednesday offered neither side in the debate over same-sex marriage a sweeping resolution. With the justices' ruling on the Proposition 8 gay-marriage ban concerning only California, the path forward nationally on the issue remains winding—and may eventually lead back to the Supreme Court.
Both sides say they are gearing up for more battles in individual states until the courts or Congress intervenes with a federal answer to a core question: Is there a federal right to marriage for same-sex couples?
Very few states remain undecided on gay marriage. Earlier this year, legislators in Rhode Island, Delaware and Minnesota decided to begin marrying same-sex couples, following ballot votes to legalize the practice last November in Maine, Maryland and Washington. In recent months, gay-rights advocates have been lobbying legislatures and governors in Illinois and New Jersey to adopt same-sex marriage this year, and expect to do so in Hawaii next year.
Beyond those places, however, 30 states have existing constitutional bans on same-sex marriage. Undoing them usually requires a ballot vote, and in many cases also the backing of the state legislature.
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Such constitutional referendums are usually lengthy and costly. In Nevada, gay-rights advocates have begun the process to challenge their state's ban on the ballot no sooner than 2016. The first state to test a constitutional ban at the ballot may be Oregon, where gay-rights advocates have submitted preliminary paperwork to get the issue on the Nov. 2014 ballot. Oregon United for Marriage, which is leading the drive to get the issue put back on the ballot, thinks the campaign will cost them some $10 million.
After Nevada and Oregon, it isn't yet clear which states might be next in the ballot challenges. "It's more art than science," said Fred Sainz, a vice president at the Human Rights Campaign.
"Whatever we thought conventional wisdom was about the more difficult states must be reassessed" in the light of fast-moving public opinion, said Kate Kendell, the executive director for the National Center for Lesbian Rights. "I think there could easily be half a dozen states" where bringing the issue back to the ballot makes sense for her side, she said.
Many gay-rights leaders said they don't intend to take individual battles to every state for years to come.
"The strategy has always been to win a critical mass of states and a critical mass of public support, which together create the climate that enables the Supreme Court to bring the country to national resolution," said Evan Wolfson, founder of New York-based Freedom to Marry. "That is the classic pattern of civil-rights advancement in America."
At some point, he said, "it will be clear to everyone, including the Supreme Court, that it is simply untenable for America to be a house divided."
For opponents of gay marriage, who were on the offensive for much of the last decade, the next phase of the battle involves playing defense in the state and courts, while continuing their to push for new constitutional amendments on the ballot in states such as Indiana, to further entrench existing bans.
"If they want to go to the ballot, we welcome that," said Brian Brown, president of the National Organization for Marriage.
Other opponents of gay marriage said they will redouble efforts to build cultural support for their cause.
"I don't think we can deny" that public opinion on the issue has shifted, said Rev. William Owens, president of the Coalition of African-American Pastors. That is partially due to the move by President Barack Obama to support gay marriage, he said, which made young people in particular feel like "our position is obsolete."
Going forward, he said, "We are going to aggressively get out in the community and support families ... to educate our young people towards what we believe to be right."
At the moment, there is no clear path for how—and if—the issue might make it back to the Supreme Court. Even as Prop 8, known as the Perry case, was being weighed by the Supreme Court, there were eight other cases pending in federal or state courts that involved challenges to gay marriage bans.
The two cases that have made the most progress through the courts are Sevcik v. Sandoval, out of Nevada, and Jackson v. Abercrombie, out of Hawaii, both of which were on pause with the Ninth Circuit Court of Appeals pending Wednesday's Supreme Court ruling.
A core issue in those cases is whether states that offer same-sex couples the civil equivalents of marriage in terms of rights—but not the term "marriage"—stand up to the equal-protection provisions in the Fourteenth Amendment of the Constitution.
And unlike California's Perry case, the Nevada case isn't clouded by potential standing issues, because the state has agreed to defend its own laws. That case could have a Ninth Circuit hearing by early next year, and a decision at some point later in the year.
Could it be the next Supreme Court case on marriage?
"We filed it, in part, to have a next case in the pipeline," said Jon W. Davidson, the legal director of Lambda Legal, one of the groups arguing the case. But he added that there are many factors at play before it ends up there.
Mr. Brown, of the National Organization for Marriage, said he thought it would be "at least a decade" before the Supreme Court took up the issue again. Meanwhile, he promised to push for national resolution with a federal marriage amendment.
Mr. Wolfson, of Freedom to Marry, doesn't think his fight will take that long. "It is a matter of years, not decades," he said.
Write to Geoffrey A. Fowler at geoffrey.fowler@wsj.com
