The sponsors of California's gay marriage ban renewed their effort Thursday to disqualify a federal judge because of his same-sex relationship, but they met a skeptical audience in an appeals court panel.

It's the first time an American jurist's sexual orientation has been cited as grounds for overturning a court decision.

Lawyers for a coalition of religious conservative groups told a three-judge panel of the 9th U.S. Circuit Court of Appeals that Chief U.S. District Judge Vaughn Walker should have revealed he had a long-term male partner before he presided over a trial on the measure's constitutionality. He also should have stated whether he had any interest in getting married, the lawyers said.

Because he did not, Walker's impartiality stands in doubt and the decision he ultimately made to strike down Proposition 8 as a violation of Californians' civil rights must be reversed, said Charles Cooper, an attorney for the ban's backers.

"In May 2009, when Judge Walker read the allegations of the complaint, he knew something the litigants and the public did not know: He knew that he, too, like the plaintiffs, was a gay resident of California who was involved in a long-term, serious relationship with an individual of the same sex," Cooper said. "The litigants did not have any knowledge of these facts, and it appears that Judge Walker made the deliberate decision not to disclose these facts."