A traditional-values group lost a bid to a U.S. appeals court in San Francisco today to become an official party defending California’s same-sex marriage ban against a federal lawsuit.

The 9th U.S. Circuit Court of Appeals rejected an appeal in which the Sacramento-based Campaign for California Families sought to become an intervenor, or party, in a lawsuit filed by two same-sex couples in May.

The lawsuit challenging the ban enacted by voters last year as Proposition 8 is scheduled to go to trial before U.S. District Judge Vaughn Walker in San Francisco on Jan. 11.

In today’s ruling, a three-judge panel of the appeals court said the interests of the campaign for California Families will be adequately represented in the case by the proponents of Proposition 8 and their committee, ProtectMarriage.com.

Judge Margaret McKeown wrote, “It is apparent to us that the ultimate objective of the campaign and the proponents is identical–defending the constitutionality of Proposition 8 and the principle that the traditional definition of marriage is the union of a man and a woman.”

McKeown added, “Any differences are rooted in style and degree, not the ultimate bottom line.”

Earlier this year, Walker ruled that the proponents of Proposition 8 could become an intervenor to defend initiative against the lawsuit.

The nominal defendants are various state and county officials, but Gov. Arnold Schwarzenegger, other state officers and county clerks have taken no position on the constitutionality of Proposition 8, and state Attorney General Jerry Brown has said he believes the measure is unconstitutional.

Later, Walker ruled that the city of San Francisco could join the case as an intervenor on the side of the two couples, but denied the Campaign for California Families and a coalition of gay community groups permission to become intervenors.

The campaign then appealed.

The campaign, like any other group with an interest in the case, still has the right to file advisory friend-of-the-court briefs.

The lawsuit was filed by Kristin Perry and Sandra Stier of Berkeley and Paul Katami and Jeffrey Zarrillo of Burbank on May 22, four days before the California Supreme Court upheld Proposition 8 as being within voters’ right to amend the state Constitution.

The couples contend the measure violates their federal constitutional rights to due process and equal treatment.

Please make sure your comment adheres to our comment policy. If it doesn't, it may be deleted. Repeat violations may cause us to revoke your commenting privileges. No one wants that!