By striking down California’s ban on same-sex marriage, a divided federal appeals court on Tuesday became the first in the nation to conclude a state has no compelling social or legal justification for denying gay and lesbian couples the right to wed.

The ruling draws the U.S. Supreme Court closer than ever into the gay marriage fray.

The 9th U.S. Circuit Court of Appeals emphatically declared voter-approved Proposition 8 to be unconstitutional. But its 2-1 ruling revealed a deep split in judicial philosophy over a state’s ability to forbid same-sex marriage, offering a preview of the possible Supreme Court debate to come.

In the interim, same-sex weddings in California are not expected to resume while Proposition 8 backers press forward with plans to appeal.

The decision upheld the ruling of former San Francisco Chief U.S. District Judge Vaughn Walker, who invalidated Proposition 8 in 2010 after an unprecedented trial.

Gay rights advocates cheered Tuesday’s ruling, conservatives from family values groups to Republican presidential candidate Mitt Romney decried it and legal experts predicted it would face equal division whenever it reaches the Supreme Court.

“Proposition 8 serves no purpose, and has no effect, other than to lessen the status and human dignity of gays and lesbians in California, and to officially reclassify their relationships and families as inferior to those of opposite-sex couples,” wrote Stephen Reinhardt, one of the nation’s most liberal judges, who was joined by Judge Michael Daly Hawkins.

In his dissent, N. Randy Smith, a conservative appointee of former President George W. Bush, concluded California has a constitutional basis to restrict the definition of marriage to a union between a man and woman. He wrote there were “legitimate governmental interests” in banning same-sex marriage, such as arguments the ban promotes procreation.

The distinction is crucial because any government-imposed restrictions on a particular group must be supported by “rational” reasons to be constitutional.

Proposition 8 backers can now ask the 9th Circuit to rehear the case with an 11-judge panel, or proceed directly to the Supreme Court. Either way, same-sex marriages will await the legal process, with further appeals likely to stretch at least into next year.

The 9th Circuit put its decision on hold for at least two weeks to give Proposition 8 supporters time to appeal, as they quickly pledged to do. Any 9th Circuit judge can also call for a vote on whether to rehear the case, which would require a majority vote of the court’s 25 full-time judges.

Andy Pugno, general counsel for Proposition 8 supporters, called the ruling a “misguided decision that disregards the will” of California voters. The group has yet to decide whether to seek further review in the 9th Circuit, although Pugno said, “Our path to the U.S. Supreme Court is now very clear.”

Theodore Olson, a lawyer for same-sex couples, expects the ruling to be put on hold, but promised to contest any stays. “Constitutional rights can’t wait any longer,” said Olson, a former U.S. solicitor general.

Legal experts were quick to note that Reinhardt steered clear of trying to create a broad fundamental right for same-sex couples to marry that might apply to other states. The 9th Circuit ruling focused on California’s circumstances, notably the fact Proposition 8 stripped away the right of same-sex couples to marry that had been established in a 2008 California Supreme Court decision. Creating separate, unequal classes of relationships is unconstitutional, Reinhardt said in the first federal appeals court ruling of its kind.

He relied heavily on the U.S. Supreme Court’s 1996 ruling, written by Justice Anthony Kennedy, striking down a Colorado law that stripped gays and lesbians of protection against discrimination. Smith, in his dissent, disputed there were similarities in the two laws, a likely focus of further appeals.

The two judges’ competing views on the Supreme Court’s gay rights precedents appeared written with an eye toward Kennedy and his expected role as a swing vote on the issue.

“It’s a strong decision, but it is not the ringing endorsement of broader marriage equality that some might have hoped for,” said Kenneth Sherrill, a Hunter College political-science professor. “Instead, it’s narrowly crafted … and I think crafted to be affirmed on an appeal to the Supreme Court.”

Added Steve Sanders, a University of Michigan law professor, “By ruling narrowly, the court said same-sex marriage remains an issue that should be decided state by state.”

Kristin Perry and Sandy Stier, a Berkeley couple seeking the right to marry, signed on to the 2009 challenge to Proposition 8. Flanked by their two sons, they expressed hope the 9th Circuit ruling is a step toward gaining the right to walk down the aisle.

“Now, Sandy and I are closer to achieving that reality,” Perry said. “We can’t wait for that day.”

The case has not affected the roughly 18,000 couples who married before voters restored the same-sex marriage ban in 2008, creating a two-tiered system of relationships for gay and lesbian couples.

Gay rights advocates argued the separate status for the state’s gay and lesbian couples underscored the legal weakness in outlawing same-sex marriage, but Proposition 8 supporters disagreed, saying the state’s strong domestic partner protections are sufficient.

The 9th Circuit resolved two other issues in the case, including finding that Proposition 8 supporters have a legal right to defend the law when the state’s top elected officials refuse to do so. The federal court said it would abide by a California Supreme Court ruling last year allowing the group to defend the law without Gov. Jerry Brown and Attorney General Kamala Harris, both of whom consider the law unconstitutional and who praised Tuesday’s ruling.

The 9th Circuit also rejected the Proposition 8 campaign’s argument that Walker’s ruling should be set aside because he was in a same-sex relationship while handling the case. Smith joined in that part of the opinion.