When U.S. District Judge Vaughn Walker struck down California's Proposition 8—the 2008 ballot initiative to outlaw gay marriage—he said the motivation for the majority of voters was clear.

"The evidence shows conclusively that moral and religious views form the only basis for a belief that same-sex couples are different from opposite-sex couples," Walker wrote in his sweeping, 136-page decision announced August 4 in San Francisco. "These interests do not provide a rational basis for supporting Proposition 8."

In Walker's reasoning, religion amounts to a "private moral view," which should not infringe upon the constitutional rights of others. While some legal scholars say Walker's decision lands on firm legal ground—a law must advance a secular purpose to pass constitutional muster—some religious leaders accuse the judge of trying to scrub faith from the public square.

On August 5, Prop 8's supporters filed an appeal of Walker's decision. Jim Campbell, an attorney with the Alliance Defense Fund, a conservative Christian law firm involved in the litigation, said the religious freedom argument will play an important role as the case moves up the federal judicial ladder—including, potentially, the U.S. Supreme Court.