Opponents have challenged the law's constitutionality and will make their case before the California Supreme Court in a three-hour hearing on March 4.
"Male-female marriage is the life-blood of community, society, and the state," wrote the brief's author, Kenneth Star, the conservative prosecutor in the President Clinton impeachment proceedings.
"We rely on this honored institution for the procreation and proper formation of the next generation. Social science demonstrates, and [our] own long experience confirms, that a child fares best when raised by caring biological parents who have the deepest stake in his or her well-being and who can provide both male and female role models."
The brief was signed by the California Catholic Conference, National Association of Evangelicals, and the Union of Orthodox Jewish Congregations of America, in addition to The Church of Jesus Christ of Latter-day Saints. Starr's co-author was Alexander Dushku, of Kirton & McConkie, the LDS Church's law firm.
The LDS Church has been involved in the California effort to promote traditional marriage since 1998, when members were asked by their local leaders to support Proposition 22, financially and personally.
"We were asked to canvass neighbors, go door to door with the petition and ask for support," said Russell Frandsen, a Latter-day Saint in southern California. "A large number of us volunteered to do that. I suppose most of us did it out of a sense of responsibility."
Soon after the bill passed, the California legislature passed a domestic partnership bill that granted all the rights of marriage through civil unions, Frandsen said. "It's marriage in all but name only."
Even during the fractious debate over Proposition 22, he said, some Mormons in southern California wrote letters to the editors of newspapers saying that although they believed marriage to be the best for society, they opposed discrimination against gays and lesbians. Unlike Peter Danzig, who was called in by LDS leaders in Utah for writing a letter, Frandsen is unaware of anyone in southern California who faced similar pressure.
"The church has actually been fairly progressive in terms of calling for polite and respectful treatment of gays and lesbians," Frandsen said. "We don't hear too much gay bashing around here."
Now there is a move in California to amend the state constitution, making Proposition 22 permanent. It is not clear whether the LDS Church will get involved again.
"I have heard nothing about it at church," Frandsen said. "There is no official church involvement in pushing the constitutional amendment yet."