SAN FRANCISCO _ A federal appeals court is expected to rule Tuesday on the constitutionality of Proposition 8, the 2008 ballot measure that banned gay marriage in California.

Regardless of how a three-judge panel of the 9th U.S. Circuit Court of Appeals decides the case, its ruling is very likely to be appealed to the U.S. Supreme Court, which could decide next year whether gays and lesbians nationwide have the right to marry.

Former Chief U.S. District Judge Vaughn R. Walker, 67, a Republican appointee, ruled in August 2010 that Proposition 8 violated the federal constitution. ProtectMarriage, the sponsors of Proposition 8, appealed his ruling to the 9th Circuit.

The appeals panel's decision is scheduled to be released by 10 a.m. PST. During arguments, the panel appeared to be leaning toward striking down the marriage ban.