No Democrats are listed on the document, which apparently was circulated individually to lawmakers.
Rep. Jennifer Seelig, D-Salt Lake City and House minority leader, said she learned there was an effort to gather signatures Monday evening after receiving an email apparently sent to her by mistake and thanking her for supporting the Republican effort.
Seelig, a member of the Utah Pride Center's board of directors, said she took immediate steps to ensure her name wasn't on the brief.
The lawmakers filed the brief after tabling any bills related to same-sex marriage or LGBT issues, including a bill sponsored by Urquhart that would ban employment and housing discrimination based on sexual orientation.
Lawmakers decided to put the bills on hold on the advice of Utah Attorney General Sean Reyes and Gene Schaerr, an attorney hired to help the state defend Amendment 3 and other state laws banning same-sex marriage.
Seelig said if lawmakers are individually signing on and the effort is being kept separate from institution processes, she doesn't have a problem with it.
That said, she added: "They are making it a partisan issue. We haven't talked about it. No one requested to talk to our caucus as a group about it. ... We haven't taken a position on it as a caucus group."
Sen. Jim Dabakis, D-Salt Lake and Democratic Party chairman, said, "no one asked me to participate. It is such a pity, as I would have had so many great suggestions."
Rep. LaVar Christensen, R-Draper, who authored Amendment 3 and was one of four lawmakers behind the brief, did not respond to an email from The Salt Lake Tribune asking about the process for collecting signatures.
Anderson said Tuesday he was "very supportive" of the position taken regarding state jurisdiction over marriage.
"I agree states should have and retain jurisdiction over marriage law," Anderson said. "However, in the short amount of time I had to read through the brief, I cannot say I supported the entire argument and therefore I felt uncomfortable signing on."
Anderson declined to elaborate on what gave him pause.
Hall said he was given the brief Monday and told he had just a couple of hours to decide whether to sign it. As an attorney, Hall said he is "extra sensitive" about signing documents he has not thoroughly reviewed and believed he did not have adequate time to go through the 32-page brief.
Cox also said he did not have enough time to review the document, though he supports Amendment 3 and will "certainly fund defending it."
Lawmakers on Tuesday briefly discussed appropriating $50,000 to replenish funds already spent in defense of the measure.
In the brief, the lawmakers argued they have a "profound duty" based on "deep historical roots and experience" that they said shows children are best served by public endorsement of, and limiting marriage to, just one man and one woman. They said the state's stance on marriage has helped contribute to Utah's unwed birthrates, high rates of children raised by both parents and high rates of upward mobility.
The lawmakers said Utah's marriage law reflects respect and empathy for all, while upholding traditional marriage. They argue that "conjectural" and "intemperate" assertions by the three same-sex couples challenging Amendment 3 and U.S. District Court Judge Robert J. Shelby that the ban is based on animus or inequality are wrong. The laws are simply designed to "endorse and encourage each child's opportunity to be reared by a married mother and father," the lawmakers said.
And Utah law does not prevent same-sex couples from forming private intimate relations, they add.
But if marriage is redefined to include same-sex couples, hundreds of statutes that endorse child rearing by a married mother and father could be affected. Among those are laws and policies dealing with premarital counseling, birth and adoption, legal parenthood, child welfare, education, marriage promotion and divorce.
"We do not believe," the brief states, "that a court, considering only the interests of plaintiffs in the case before it, should intrude into the state's domestic relations authority by attempting a redefinition of marriage that would entail such profound, far-reaching and unconsidered consequences."
Sixteen Utah counties also submitted a brief Monday in support of the state's same-sex marriage ban: Juab, Beaver, Box Elder, Cache, Emery, Garfield, Iron, Kane, Millard, Morgan, Sanpete, Sevier, Uintah, Utah, Wasatch and Washington counties.
A majority of participating voters in all but two of Utah's 29 counties cast ballots in favor of Amendment 3 in 2004. The measure failed in Grand and Summit counties.
Voters in the 16 counties, represented by Brigham Young University law professor Lynn D. Wardle and Juab County Attorney Jared W. Eldridge, were heavily in favor of Amendment 3.
Nearly 80 percent of Utah County voters who participated in the general election approved the amendment, while it was passed by a 64 percent of voters in Wasatch County, the lowest margin among the counties.
"The interest in this case of these amici counties is to voice the view of their counties that protection of marriage as the union of a man and a woman is important, and that the laws of the state of Utah so defining marriage are basic civil rights laws protecting the core social institution of society and the values upon which our constitutional government and liberties rest," the counties said in their brief.
They argue "family law was constitutionally to remain subject to state, not national regulation." If federal law must respect state policies that permit same-sex marriage, it also must respect state laws that do not permit such unions.
"Our federalism encourages diversity," the counties said, "allowing some states to experiment with new forms of marriage, while protecting other states that chose instead to strengthen and preserve traditional marriage."
They also said the three same-sex marriage couples who sued Utah over Amendment 3 are engaged in an "illegitimate attempt to capture marriage for the purpose of promoting another philosophy and policy extraneous to the purpose of marriage."
In all, nearly two dozen groups or individuals, ranging from social science academics to a faith coalition that includes The Church of Jesus Christ of Latter-day Saints, have filed amicus briefs.
Utah, which filed its opening brief Feb. 3, is seeking to overturn Shelby's Dec. 20 decision that found the state's ban on same-sex marriage to be unconstitutional. The 10th Circuit has set oral arguments in the Utah case for April 10, and in a similar Oklahoma case for April 17.