In a San Francisco courtroom yesterday, the chief judge of the federal district court, Vaughn R. Walker, handed down his long-awaited ruling in the challenge to the constitutionality of California’s Proposition 8, the measure that embraced the definition of marriage in the Defense of Marriage Act (DOMA) and thus ended the state recognition of gay marriages in California. Judge Walker announced that Proposition 8 was unconstitutional, violating both the equal protection and due process clauses of the constitution.

On Fox News the decision was instantly derided as the act of another “liberal activist” judge. That label hardly fits: Walker was appointed by Presidents Reagan and Bush (father), and his Republican and conservative credentials are beyond dispute. But Walker belongs to the libertarian, law-and-economics branch of the G.O.P., not the socially conservative, religious-right branch. His decision in the Proposition 8 case, Perry v. Schwarzenegger, is extremely powerful and goes straight to the core of the matter:

The right to marry has been historically and remains the right to choose a spouse and, with mutual consent, join together and form a household. Race and gender restrictions shaped marriage during eras of race and gender inequality, but such restrictions were never part of the historical core of the institution of marriage. Today, gender is not relevant to the state in determining spouses’ obligations to each other and to their dependents. Relative gender composition aside, same-sex couples are situated identically to opposite-sex couples in terms of their ability to perform the rights and obligations of marriage under California law. Gender no longer forms an essential part of marriage; marriage under law is a union of equals.

Walker’s opinion is carefully crafted. In the American legal system, special authority is given to the trial judge, sitting without a jury, as a finder of fact. In theory, determinations of law can always be reexamined from scratch by the appellate courts. But that’s not the case with respect to the facts. The trial judge has an opportunity to examine witnesses and determine based on a variety of factors whether the witnesses are telling the truth. His determinations will only be second-guessed in extraordinary cases. Walker has used this authority to its best advantage to shore up his conclusions—he reviews the fact evidence submitted by the Proposition 8 proponents and their adversaries with extraordinary care.

Proposition 8 was largely (and covertly) funded by groups and individuals associated with the Mormons and a handful of religious-right evangelical groups. While their spending on the election was substantial, the effort to defend the result in court was an open embarrassment. Designated witnesses for Proposition 8 defected and renounced their own views under questioning, and those that survived the process effectively exposed the dubious underpinnings of Proposition 8 advocacy with their own evidence. By contrast, the effort to overturn Proposition 8 was led by a bipartisan dream team consisting of George W. Bush’s and Al Gore’s attorneys from the 2000 election campaign, Ted Olson and David Boies. They demolished their adversaries and put on an airtight case of their own. More than 70 percent of the opinion consists of a review of the factual contentions at the end of which the court adopted the view that most independent observers had: the Proposition 8 case rested on a shaky foundation of falsehoods and bigotry.

The case will now proceed to the Court of Appeals. The question of the constitutionality of DOMA itself will also eventually find its way to the Supreme Court, though not necessarily through this case. How the case progresses will largely rest in the hands of Republican judges, who compose almost two-thirds of the federal bench. Will they tilt in the direction that Karl Rove ordained, upholding DOMA and thus keeping the issue alive for future election cycles? A year ago, that would have been the broad expectation. But gay marriage has gotten surprising support from conservative and Republican judges. Judge Walker is one case, but, as Andrew Sullivan notes, the recent federal court opinion in Massachusetts holding DOMA unconstitutional was rendered by Nixon appointee Joseph Tauro, and the historic judgment of the Republican-dominated Supreme Court of Iowa was authored by Republican Justice Mark Cady. Public opinion polling shows that outside of the Old Confederacy and the Mormon belt in the West, where unalloyed bigotry is always an effective electoral tactic, the once vital issue no longer resonates for the G.O.P. Will the Party of No accept the signal that Republican judges and lawyers are sending it—namely, that it’s time to find some new hot-button issues?