Thirty-one social conservative groups have joined the fight to keep California's gay marriage ban, Proposition 8.

The groups have united against an August ruling that declared the ban unconstitutional and is being appealed to the Ninth Circuit Court of Appeals by its sponsor,, a coalition of social conservative groups that includes the Church of Jesus Christ of Latter-day Saints (the Mormons), the California Catholic Conference and various evangelical churches.

In the amicus brief filed Thursday, the groups argue that “initiatives promote the will of the people better than government solely by the elite.”

“The people may be wrong, as they often are,” the brief says. “The courts, too, may be wrong, as they often are. But this we know: Twice in eight years the people of California declared they want to keep marriage as it has been for time immemorial.”

Signing onto the brief are the Liberty Institute, Association of Maryland Families, California Family Council, Center for Arizona Policy, Citizens for Community Values, Cornerstone Action, Cornerstone Family Council, Delaware Family Policy Council, Family Action Council of Tennessee, the Family Foundation, the Family Policy Council of West Virginia, Family Policy Institute of Washington, Florida Family Policy Council, Georgia Family Council, Illinois Family Institute, Independence Law Center, Iowa Family Policy Center, Louisiana Family Forum Action, Massachusetts Family Institute, Michigan Family Forum, Minnesota Family Council, Missouri Family Policy Council, Montana Family Foundation, New Jersey Family First, New Jersey Family Policy Council, North Carolina Family Policy Council, Oklahoma Family Policy Council, Oregon Family Council, Palmetto Family Council, Pennsylvania Family Institute, Wisconsin Family Action and WyWatch Family Action.

Proposition 8 was approved by a narrow majority of Californians in 2008. Passage put an end to the gay weddings taking place in the state after the California Supreme Court legalized the institution.

The case of Perry vs. Schwarzenegger is the first to challenge the constitutionality of a gay marriage ban. Plaintiffs – a gay couple and a lesbian couple who wish to marry – are being represented by the American Foundation for Equal Rights (AFER), a group formed to support the case. A recent New York City fundraiser hosted by former RNC Chair Ken Mehlman netted $1.2 million for the case.

In a separate brief, ten states have united in support of the ban.