[Updated at 1:26 p.m. ET] California's voter-approved ban on same-sex marriage violates the U.S. Constitution, a federal appeals court in San Francisco ruled Tuesday.

The decision by a three-judge panel of the 9th U.S. Circuit Court of Appeals is expected to be appealed, to either the full court or to the U.S. Supreme Court. But supporters of same-sex marriages cheered the decision when it was announced outside the courthouse Tuesday morning.

The 2-1 decision found the ban - known as Proposition 8 - "served no purpose, and had no effect, other than to lessen the status and human dignity of gays and lesbians in California, and to officially reclassify their relationship and families as inferior to those of opposite-sex couples." That violates the 14th Amendment's guarantee of equal protection under the law, the decision states.

The 9th Circuit, in a hearing just over a year ago, indicated it was inclined to toss out Proposition 8. The court also rejected arguments by supporters of the ban that now-retired federal judge Vaughn Walker - who found Proposition 8 unconstitutional in 2010 - should have recused himself and let another judge hear the case.

Walker disclosed after his retirement that he is gay and in a long-term relationship, leading Proposition 8 advocates to argue he should have stepped aside.

California's Supreme Court had allowed same-sex marriages in California. But Proposition 8 passed with 52% of the vote in 2008, bringing an end to the practice.

Prior to Walker's ruling, the California Supreme Court allowed that initiative to stand, saying it represented the will of the people.