A federal judge Tuesday refused to nullify a gay judge's ruling that California's same-sex marriage ban is unconstitutional. The voter-approved ban, known as Proposition 8, was enacted in 2008 and stripped gays and lesbians of the right to marry. In August, then-Chief US District Judge Vaughn Walker overturned the measure, ruling that it discriminated on the basis of sexual orientation and gender. Attorneys for proponents of the ban argued in court this week that the ruling should be thrown out because Walker failed to disclose his long-term relationship with another man. Walker had an obligation to reveal he had a longtime male partner, the attorneys said, so they could question him about possible bias. But in a 21-page opinion issued Tuesday afternoon, Chief US District Judge James Ware disagreed. "The presumption that Judge Walker, by virtue of being in a same-sex relationship, had a desire to be married that rendered him incapable of making an impartial decision, is as warrantless as the presumption that a female judge is incapable of being impartial in a case in which women seek legal relief," Ware wrote. The legal effort to disqualify Walker based on his sexual orientation is believed to be the first of its kind in US legal history. In past decades, judges have sometimes been accused of bias because of issues involving ethnicity or gender. Walker's sexual orientation and decade-long relationship were reported by local media during the trial. The former jurist spoke publicly about both after retiring earlier this year and said he never considered stepping down because he was gay. Proposition 8 amended the California constitution to define marriage as between one man and one woman. The ban remains in place while an appeal of Walker's ruling is pending. Only a handful of US states currently allow same-sex marriage. The Proposition 8 case is expected to ultimately be decided by the US Supreme Court, where it could set policy for the nation.