(CNN) -- A federal appeals court in San Francisco on Wednesday refused again to allow same-sex marriages in California while a case on the issue works its way through the courts.

Last year, a federal judge declared that Proposition 8, a voter-approved measure banning same-sex marriages in California, was unconstitutional.

The civil rights challenge is now at the U.S. Court of Appeals for the 9th Circuit, where the issue is still unresolved.

Several gay and lesbian couples asked the court to be allowed to wed in the meantime. However, the three-judge appellate panel issued a brief order Wednesday that rejected the motion "at this time."

Specifically, the panel refused to lift a stay on the order declaring Proposition 8 unconstitutional that was issued by the appeals court last December.

In the December ruling, the 9th Circuit Court of Appeals set aside the federal judge's decision that would have permitted same-sex marriages to resume in California.

At the same time, the appeals court set a fast schedule to hear the merits of the constitutional challenge to Proposition 8, the 2008 initiative defining marriage as only between one man and one woman. A decision by the appeals court is expected later this year.

The case has had an up-and-down series of rulings and referendums. The state's high court had allowed same-sex marriage, but then the voter referendum two years ago passed with 52 percent of the vote. The California Supreme Court subsequently allowed that initiative to stand, saying it represented the will of the people.

Opponents of the law next filed a federal challenge, saying the law violated 14th Amendment constitutional protections of due process and equal protection.

Judge Vaughn Walker agreed on August 4, issuing a 136-page opinion that concluded, "Proposition 8 fails to advance any rational basis in singling out gay men and lesbians for denial of a marriage license."

Walker, who was appointed to the federal bench by President George H.W. Bush, added, "Proposition 8 does nothing more than enshrine in the California Constitution the notion that opposite-sex couples are superior to same-sex couples."

Same-sex marriage is currently legal in five states and in the District of Columbia, while civil unions are permitted in New Jersey. The five states are Massachusetts, Connecticut, Vermont, Iowa, and New Hampshire.

Walker's landmark ruling assured a swift federal appeal that ultimately may reach the Supreme Court. One sticking point could be whether Proposition 8 supporters in court -- all private citizens and groups -- have legal "standing" to continue appealing the case.

State officials, including the governor and attorney general, support individual same-sex couples challenging the law. Such state "actors" traditionally defend voter referendums and legislation.

Some legal experts say if the appeals court eventually rules Proposition 8 backers cannot bring their petition for relief, the Supreme Court may not seek to intervene further, giving no clear guidance on the larger question of the constitutionality of same-sex marriage nationwide.

The high court, in a 1997 unrelated appeal, had expressed "grave doubts" about the ability of such private groups to challenge rulings that strike down ballot initiatives.

Walker's ruling had given the losing side a chance to appeal, and he held off allowing same-sex marriages from resuming until an emergency injunction request could be decided by the higher court.

The case is Perry v. Schwarzenegger (10-16696).