SAN FRANCISCO — A federal appeals court on Tuesday declared California’s same-sex marriage ban to be unconstitutional, putting the bitterly contested, voter-approved law on track for likely consideration by the U.S. Supreme Court.

A three-judge panel of the 9th U.S. Circuit Court of Appeals ruled 2-1 that a lower court judge correctly interpreted the U.S. Constitution and Supreme Court precedents when he declared in 2010 that Proposition 8 was a violation of the civil rights of gays and lesbians.

The court said gay marriages cannot resume in the state until the deadline passes for Proposition 8 sponsors to appeal to a larger panel of the 9th Circuit. If such an appeal is filed, gay marriages will remain on hold until it’s resolved.

Lawyers for Proposition 8 sponsors repeatedly have said they would consider appealing to a larger panel of the court and then the U.S. Supreme Court if they did not receive a favorable ruling from the 9th Circuit.

“Although the Constitution permits communities to enact most laws they believe to be desirable, it requires that there be at least a legitimate reason for the passage of a law that treats different classes of people differently. There was no such reason that Proposition 8 could have been enacted,” the ruling states.

In a statement issued shortly after the ruling was released Tuesday morning, the National Organization for Marriage predicted the decision would be overturned.

“Never before has a federal appeals court — or any federal court for that matter — found a right to gay marriage under the U.S. Constitution,” said John Eastman, NOM chairman and a scholar of constitutional law. “The 9th Circuit Court of Appeals is the most overturned circuit in the country, and Judge Stephen Reinhardt, the author of today’s absurd ruling, is the most overturned federal judge in America. Today’s ruling is a perfect setup for this case to be taken by the U.S. Supreme Court, where I am confident it will be reversed.”

NOM raised large amounts of money for the Proposition 8 campaign and the successful effort in 2009 that repealed Maine’s same-sex marriage law passed by a Democratic Legislature and signed into law by Gov. John Baldacci, a Democrat.

The decision is not expected to affect the proposed referendum question that would allow Mainers to vote on whether to allow same-sex marriages in the Pine Tree State.

“We should pause for a moment — but only for a moment — to celebrate this momentous decision,” Shenna Bellows, executive director of the American Civil Liberties Union of Maine, said in an email. “Then it’s time to get back to work to fight for marriage equality here in Maine. Loving committed couples in Maine deserve nothing less.”

“We applaud this ruling and the hard work of everyone involved,” Betsy Smith, executive director of Equality Maine, the group that coordinated efforts to gather signatures to get a question on the ballot, said Tuesday afternoon. “Only marriage gives couples the tools and the security to build a life together and to protect their families. In Maine our best path to marriage for the thousands of loving, committed same-sex couples here is through the ballot box, and we’re working hard to achieve that this November.”

Carroll Conley, head of the Christian Civic League of Maine, said he was disappointed but not surprised by Tuesday’s ruling. Conley,whose organization opposes same-sex marriage, predicted the U.S. Supreme Court would not sanction same-sex marriage.

“The legal team’s arguments for natural marriage aligned with every other federal appellate and Supreme Court decision on marriage in American history,” he said in an email. “While this is purportedly a constitutionally narrow decision, we recognize it could have sweeping implications; however, I don’t see this case affecting the attempt to redefine marriage in Maine.”

Brian Souchet of the Roman Catholic Diocese of Portland, which opposes the legalization of same-sex marriage, said the ruling does not change the definition of marriage.

“Marriage is not a construct of the state; the state only chose to recognize the institution of marriage for what it is, an institution that unites a man and a women with each and any children born from their union,” he said in an email. “Court rulings such as this only serve to obscure the objective reality of marriage. They cannot eliminate it.”

The legal team’s arguments for natural marriage aligned with every other federal

appellate and Supreme Court decision on marriage in American history. While this is purportedly a ‘constitutionally narrow’ decision, we recognize it could have sweeping implications; however, I don’t see this case affecting the attempt to redefine marriage in Maine.

The 9th Circuit panel crafted a narrow decision that applies only to California, even though the court has jurisdiction in nine Western states. California is the only one of those states where the ability for gays to marry was granted then rescinded.

“Whether under the Constitution same-sex couples may ever be denied the right to marry, a right that has long been enjoyed by opposite-sex couples, is an important and highly controversial question,” the court said. “We need not and do not answer the broader question in this case.”

The panel also said there was no evidence that former Chief U.S. Judge Vaughn Walker was biased and should have disclosed before he issued his decision that he was gay and in a long-term relationship with another man.

The ruling came more than a year after the appeals court heard arguments in the case.

Proposition 8 backers had asked the 9th Circuit to set aside Walker’s ruling on both constitutional grounds and because of the thorny issue of the judge’s personal life. It was the first instance of an American jurist’s sexual orientation being cited as grounds for overturning a court decision.

Walker publicly revealed he was gay after he retired. However, supporters of the gay marriage ban argued that he had been obliged to previously reveal if he wanted to marry his partner — like the gay couples who sued to overturn the ban.

Walker’s successor as the chief federal judge in Northern California, James Ware, rejected those claims, and the 9th Circuit held a hearing on the conflict-of-interest question in December.

California voters passed Proposition 8 with 52 percent of the vote in November 2008, five months after the state Supreme Court legalized same-sex marriage by striking down a pair of laws that had limited marriage to a man and a woman.

The ballot measure inserted the one-man-one-woman provision into the California Constitution, thereby overruling the court’s decision. It was the first such ban to take away marriage rights from same-sex couples after they had already secured them and its passage followed the most expensive campaign on a social issue in the nation’s history.

The Williams Institute on Sexual Orientation and the Law, a think tank based at the University of California, Los Angeles, has estimated that 18,000 couples tied the knot during the four-month window before Proposition 8 took effect. The California Supreme Court upheld those marriages, but ruled that voters had properly enacted the law.

With same-sex marriages unlikely to resume in California any time soon, Love Honor Cherish, a gay rights group based in Los Angeles, plans to start gathering signatures for a November ballot initiative asking voters to repeal Proposition 8.

BDN writer Judy Harrison contributed to this report.