The full list of current and former Republican lawmakers signing the brief won't be available until it's officially sent to the court later Tuesday, but Gallagher said many prominent Republicans are re-examining their stance on gay marriage.
The group call themselves "conservatives, moderates and libertarians who embrace the individual freedoms protected by our Constitution," embrace Reagan's idea of the Republican Party being a "big tent," and shareGoldwater's belief that the party shouldn't "seek to lead anyone's life for him," according to a copy of the brief provided to The Associated Press.
"It is precisely because marriage is so important in producing and protecting strong and stable family structures that (we) do not agree that the government can rationally promote the goal of strengthening families by denying civil marriage to same-sex couples," the argument says in the conclusion.
Washington, D.C., and 17 states, mostly in the Northeast, allow same-sex marriage. Others may soon follow depending on how federal appeals courts, and eventually the U.S. Supreme Court, rule on state bans that have been overturned.
Including Utah and Oklahoma, six federal judges have issued pro-gay-marriage rulings since the Supreme Court's decision in Windsor v. U.S. in June that struck down part of the federal anti-gay-marriage law. The latest came last week in Texas.
In Kentucky, Gov. Steve Beshear, a Democrat, announced Tuesday the state will hire outside attorneys to appeal a judge's decision granting legal recognition to same-sex couples married in other states and countries. That came as the state's attorney general, also a Democrat, announced that he would not pursue the case further.
Democratic attorneys general in at least seven states — Virginia, Pennsylvania, California, Illinois, Oregon, Kentucky and Nevada — have declined to defend same-sex-marriage bans that have been challenged in court by gay couples.
U.S. Attorney General Eric Holder said last week that his state counterparts are not obligated to defend local laws banning same-sex marriage if they believe the laws violate the U.S. Constitution.
The gay marriage bans in Utah and Oklahoma were passed by voters in 2004. They were overturned by separate federal judges in each state within a month of each other in December and January.
The Denver-based 10th U.S. Circuit Court of Appeal has assigned the same panel of judges to review both cases, which are on a fast track, but has decided to hold two different hearings. The court will discuss Utah's case on April 10 and Oklahoma's on April 17.
The appeals court must decide if it agrees with the federal judges in Utah and Oklahoma who ruled that the bans violate gay and lesbian couples' rights to due process and equal protection under the 14th Amendment.
Dozens of groups are expected to file friend of the court briefs before the Tuesday midnight deadline. The American Military Partner Association and American Sociological Association have already filed.
The American Psychological Association and a group of religious organizations that include groups representing Episcopal, Unitarians and Methodists also plan to file briefs. The religious coalition includes Mormons for Equality, a group of members of The Church of the Jesus Christ of Latter-day Saints pushing the faith to give fair and adequate treatment to gay and lesbian members.
Utah Attorney General Sean Reyes has vowed to continue defending the ban, and the state has hired outside attorneys to fight their case, which could cost up to $300,000.
In making its case for gay marriage, Tuesday's filing from the Republican group points to decades-old words from Goldwater, the longtime U.S. senator from Arizona who aggressively advocated for conservative principles. He died in 1998. The group cited this passage from his 1960 paper, "The Conscience of a Conservative."
"For the American Conservative, there is no difficulty in identifying the day's overriding political challenge: it is to preserve and extend freedom," it said. "As he surveys the various attitudes and institutions and laws that currently prevail in America, many questions will occur to him, but the Conservative's first concern will always be: Are we maximizing freedom?"
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