Even as proponents of California's gay marriage ban, Proposition 8, vow to appeal, gay marriage supporters say overturning the ruling will be difficult.

The ruling, handed down Wednesday by Chief U.S. District Judge Vaughn Walker, says Proposition 8 violates the constitutional rights of gay and lesbian couples who wish to marry.

“Because Proposition 8 prevents California from fulfilling its constitutional obligation to provide marriages on an equal basis, the court concludes that Proposition 8 is unconstitutional,” Walker wrote.

“One of the things that the judge has done is he's made a very, very strong opinion that's very difficult to overturn on appeal,” lead attorney David Boies said Wednesday night during an appearance on MSNBC's The Rachel Maddow Show.

California voters approved the measure by a narrow margin on November 4, 2008. The law put an end to gay and lesbian weddings taking place in the state after the California Supreme Court legalized the institution.

“Only a trial court [like Walker's] can make factual findings,” lawyer Brian Devine said in his analysis, adding that Walker devotes 109 pages of his 138-page ruling to factual findings.

“A Court of Appeal must give great deference to the factual findings of the trial court, especially when those findings are based on the credibility of witness testimony.”

“We should be grateful to Judge Walker for carefully and diligently going through the facts of the case, creating a detailed and compelling record for the Court of Appeal and the Supreme Court,” he added.

Douglas NeJaime, associate professor of law at Loyola Law School in Los Angeles, went further.

In an email to On Top Magazine, NeJaime said Walker concluded, based on the facts, that “Proposition 8 could not withstand the lowest level of constitutional scrutiny since ... it is based on the idea that same-sex couples (and their relationships) are inferior to different-sex couples (and their relationships).”

“Judge Walker issued several findings of fact, based on extensive expert testimony, to support these legal conclusions,” he added. “Indeed, in a statement that will likely resonate for years to come, Judge Walker concluded that '[t]he evidence shows that, by every available metric, opposite-sex couples are not better than their same-sex counterparts; instead, as partners, parents and citizens, opposite-sex couples and same-sex couples are equal.'”

Walker heard 13 days of testimony during a January trial held in a San Francisco courtroom. Closing arguments were presented in June. He's stayed his ruling at least until Friday, when he'll hold another hearing to determine if gay marriages can resume as the case is being appealed.

Andy Pugno, lead counsel for Protect Marriage, the group that sponsored Proposition 8, called the decision “a disappointment.”

“The judge's invalidation of the votes of over seven million Californians violates binding legal precedent and short-circuits the democratic process,” he said. “But this is not the end of our fight to uphold the will of the people for traditional marriage, as we now begin an appeal to the Ninth Circuit Court of Appeals.”

“We will certainly appeal this disappointing decision,” Brian Raum, senior counsel at the Alliance Defense Fund (ADF), whose attorneys defended Proposition 8, said. “Its impact could be devastating to marriage and the democratic process.”