A federal appeals court was due to begin hearing a case on California’s gay marriage ban today.

The Ninth US Circuit Court of Appeals in San Francisco will hear arguments around a federal judge’s ruling that the ban on gay marriage in the state is unconstitutional.

In August, Chief US District Judge Vaughn Walker ruled that the ban, also known as Proposition 8, violates equal protection clauses in the US constitution and that moral disapproval is not a valid reason to deny the right to marry.

A three-judge panel was selected at random to hear the case. They are Judge Michael Hawkins, a moderate Democratic appointee; Judge Stephen Reinhardt, a liberal; and Judge N Randy Smith, a conservative.

Gay marriage was legal in the state for just a few months in 2008 before voter initiative Proposition 8 reinstated the ban.

The judges will consider whether the ban on gay marriage is constitutional.

They will also consider whether the anti-gay groups have the legal standing to bring the case to court.

As state officials, California governor Arnold Schwarzenegger and Attorney-General Jerry Brown were the legal defendants in the case but both have refused to support the ban, with Mr Brown calling it unconstitutional.

This leaves anti-gay groups in the unusual position of defending the law as ordinary citizens.

The case may proceed as far as the Supreme Court.

Judge Walker made his ruling in August, following a three-week trial in the spring.

Gay marriages were to resume a week later and couples began planning their ceremonies but opponents successfully argued at the 9th District Court of Appeals that the ban should stay in place until they have appealed.