(San Francisco, California) Religious leaders and labor unions have joined the call for the Supreme Court of California to invalidate Proposition 8, the amendment to the state constitution approved in November by voters that restricts marriage to opposite-sex couples.

The California Council of Churches and other religious leaders and faith organizations representing millions of members filed a friend of the court brief arguing the measure violates the civil rights of gay citizens.

In addition to the council, the group includes the General Synod of the United Church of Christ, two Episcopal Bishops, the Progressive Jewish Alliance, the Unitarian Universalist Association of Congregations and the Northern and Southern California Nevada Conferences of the United Church of Christ.

A second brief will be submitted Friday by a coalition of more than 50 California labor organizations, including United Healthcare Workers and the California Labor Federation. In total, the labor organizations represent more than two million working men and women in California.

“This is a very significant brief from California’s labor unions,” said Shannon Price Minter, Legal Director of the National Center for Lesbian Rights. NCLR along with Lambda Legal and the ACLU have challenged the constitutionality of Prop 8.

“These unions represent more than 2 million working men and women in California. They have many members who are gay, lesbian, bisexual and transgender, and they support the rights of all their members to be treated fairly and equally under the California Constitution,” Minter said in a statement.

The union brief echoes arguments made by NCLR and the other litigants that Prop 8 is invalid because it is not a “constitutional amendment,” but a “constitutional revision.”

A revision requires a two-thirds vote of the Legislature to get on the ballot, while an amendment can go on the ballot as Prop 8 did through the collecting of  signatures.

“If a simple majority of voters can take away one fundamental right, it can take away another,” the union brief argues. “If it can deprive one class of citizens of their rights, it can deprive another class too. Today it is gays and lesbians who are singled out. Tomorrow it could be trade unionists.”

The umbrella group of social conservatives and conservative churches, Yes on 8, have told the court that it should not overturn the will of the people.

Prop 8 passed in November by a slim 52 percent. The Supreme Court is expected to hear oral arguments in the case in March.

California Attorney General Jerry Brown also has called for the measure to be overturned. Brown’s office submitted its brief in December, arguing the measure should be invalidated because it deprives people of the right to marry—an aspect of liberty that the Supreme Court has concluded is guaranteed by the California Constitution.

The issue of same-sex marriage in California dates back to 2004 when San Francisco mayor Gavin Newsom began issuing marriage licenses to same-sex couples.  Some 8,000 couples exchanged vows before the state Supreme Court ruled Newsom had acted illegally.

The court nullified the marriages but said its ruling dealt only with Newsom’s actions.  The justices said at the time the question of whether barring same-sex couples from marrying violated the state’s equal protection clause of its constitution was a separate matter.

Legal challenges on the constitutional question were begun almost immediately. Three separate suits ultimately were wrapped together into a single case.

In March 2005, a Superior Court judge in San Francisco ruled that the law denying same-sex marriage was unconstitutional.

“It appears that no rational purpose exists for limiting marriage in this state to opposite-sex partners,” County Superior Court Judge Richard Kramer said in a written ruling.

In striking down the state ban on same-sex marriage Kramer wrote that the state’s historical definition of marriage, by itself, cannot justify the denial of equal protection for gays and lesbians.

Kramer stayed his ruling while the state appealed.

In October 2006, the California Court of Appeal in a split decision overturned Kramer’s ruling.

Last May, the state Supreme Court upheld the appeal court ruling and thousands of same-sex couples began marrying.

The Yes on 8 campaign immediately began collecting signatures for the voter initiative.  The group also wants the court to annul the 18,000 same-sex marriages that took place before the vote.