Court: Calif. ban on gay marriage is unconstitutional A three-judge panel from the 9th U.S. Circuit Court of appeals has ruled that California's Proposition 8 violates the rights of gays and lesbians, and is therefore unconstitutional. NBC's Pete Williams reports. SAN FRANCISCO -- A federal appeals court has declared California's Proposition 8 unconstitutional, paving the way for a likely U.S. Supreme Court showdown on the voter-approved law. A three-judge panel of the 9th U.S. Circuit Court of Appeals ruled 2-1 that a lower court judge correctly interpreted the U.S. Constitution when he declared in 2010 that Proposition 8 was a violation of the civil rights of gays and lesbians. "Proposition 8 serves no purpose, and has no effect, other than to lessen the status and human dignity of gays and lesbians in California, and to officially reclassify their relationships and families as inferior to those of opposite-sex couples," said Judge Stephen Reinhardt in the majority opinion. The Constitution simply does not allow for 'laws of this sort'. Read the full decision from the 9th U.S. Circuit Court of Appeals Although the Constitution permits communities to enact most laws they believe to be desirable, it requires that there be at least a legitimate reason for the passage of a law that treats different classes of people differently. There was no such reason that Proposition 8 could have been enacted," the ruling stated. The passage of the ban followed the most expensive campaign on a social issue in U.S. history. Lawyers for Proposition 8 sponsors and for the two couples who successfully sued to overturn the ban have said they would consider appealing to a larger panel of the court and then the U.S. Supreme Court if they did not receive a favorable ruling. Opponents of Proposition 8 celebrate outside of the 9th U.S. Circuit Court of Appeals on Tuesday in San Francisco. About 50 people outside the San Francisco courthouse cheered and some waved flags when the decision was announced. About an hour after the ruling was published on the court's website, ProtectMarriage.com vowed to appeal. "Ever since the beginning of this case, we've known that the battle to preserve traditional marriage will ultimately be won or lost not here, but rather in the U.S. Supreme Court," Andy Pugno, general counsel for the ProtectMarriage.com coalition, said in a statement. We will immediately appeal this misguided decision that disregards the will of more than 7 million Californians who voted to restore marriage as the unique union of only a man and woman. Gay marriages probably will remain on hold in California until the appeals process ends. The court made clear in Tuesday's ruling that proponents of the ballot measure have the right to appeal a decision regarding that measure in court. The case was pending for months because the court wanted a ruling from the state Supreme Court on whether proponents of Proposition 8 had legal standing under the state's citizen's initiative process to appeal the ruling. The timeline of events leading to Tuesday's announcement stretches back to March 2000, when California voters backed Prop. That ballot measure stated that marriages between a man and a woman are valid in California, but the state Supreme Court ruled eight years later that the law was unconstitutional and because it discriminated against gays. That led opponents of same-sex marriage to place Prop. 8 on the November 2008 ballot. It was approved by a margin of 52.5 percent to 47.5 percent. Four-month window An estimated 18,000 couples married during the four-month window after the Supreme Court ruling and before Prop. 8 went into effect, according to the Williams Institute on Sexual Orientation and the Law. A California Supreme Court ruling upheld those marriages. The case landed in federal court, and U.S. District Judge Vaughn Walker ruled in August 2010 that Prop. 8 "both unconstitutionally burdens the exercise of the fundamental right to marry and creates an irrational classification on the basis of sexual orientation." His ruling prompted an appeal by Prop. 8 supporters, which led to Tuesday's ruling by the three-judge panel that heard arguments in December. Attorneys for ProtectMarriage.com argued that California voters who supported Proposition 8 should not be invalidated "based on just one judge's opinion." But the appeals court ruled Tuesday that " (Prop. 8) stripped same-sex couples of the ability they previously possessed to obtain from the State, or any other authorized party, an important right -- the right to obtain and use the designation of 'marriage' to describe their relationship. Nothing more, nothing less. The court ruled Tuesday that Prop. 8's "only effect was to take away that important and legally significant designation." Supporters of Prop. 8 also asked that Walker's ruling be thrown out because the judge was in a same-sex relationship that he had not disclosed. A denial of that motion was affirmed by the court's ruling Tuesday. "With the sponsorship of the Hollywood elite, this lawsuit has been pushed forward as an assault on traditional marriage, with the help of a judge who failed to disclose his own long-term homosexual relationship while presiding over a case seeking the legalization of same-sex marriage," Pugno, the attorney for ProtectMarriage.com, said. Judge N. Randy Smith wrote in his dissent that he was "not convinced that Proposition 8 is not rationally related to a legitimate governmental interest" in restricting the definition of marriage to a union bewteen a man and woman. NBCSanDiego.com's Jonathan Lloyd and The Associated Press contributed to this report.