During an hour-long argument, two of the three judges on the panel scrutinized the position of the lawyer for Utah that society at large and children in particular benefit from marriages exclusively between a man and a woman.
The hearing before the 10th U.S. Circuit Court of Appeals was the first at a regional U.S. appeals court since a U.S. Supreme Court ruling last June forced the federal government to extend benefits to same-sex couples married in states that allow gay marriage.
Unlike the landmark ruling on federal benefits, the cases making their way through the courts now raise a more fundamental question: Does the Constitution extend to same-sex couples the same right to marry that opposite-sex couples have?
To date eight U.S. district court judges have interpreted last June's ruling to favor same-sex marriage. It is likely that Thursday's case or related ones soon to be heard at the appeals court level could reach the ideologically divided Supreme Court by the end of the year.
Oral arguments, like Thursday's, offer a limited snapshot of judges' positions and their views could evolve when they begin to write opinions.
Judge Jerome Holmes, a Republican appointee and the first African American on the 10th Circuit bench, compared the ban on same-sex marriage to prohibitions on interracial marriage invalidated by the Supreme Court in the landmark 1967 Loving v Virginia decision.
"Why is this any different?" he asked.
While skeptical of the state position, Holmes posed hard questions to the lawyer for the challengers about how far the Supreme Court decision known as U.S. v Windsor could be taken.
Judge Carlos Lucero, a Democratic appointee, said that although the Supreme Court's decision tested federal government policy against gay marriages, the ruling suggested that principles of constitutional equality and due process would cover state government action as well.
A total of 17 states plus the District of Columbia allow same-sex marriage; 33 states do not.
Judge Paul Kelly, a Republican appointee who presided over the hearing, appeared more sympathetic to the state's position.
Kelly noted that Utah's ban, known as Amendment 3, was approved by voters and that same-sex marriages were new enough that evidence about their impact on families may not be fully known. He questioned whether a full-fledged trial should first be held on evidence related to the benefits and harms of same-sex unions.
"Can the court make the determination based on a bunch of sociological" submissions in filings? he asked.
More than 100 people, about 30 of them reporters, filled the main courtroom and 85 other spectators watched on a video screen in an overflow courtroom at the courthouse in downtown Denver.
MORE TO COME
In the Utah dispute, U.S. District Court Judge Robert Shelby ruled the Utah ban violates constitutional guarantees of equal protection and due process. Invoking the language of Windsor, he said it "places same-sex couples in an unstable position of being in a second-tier relationship."
The same 10th Circuit three-judge panel is expected to hear a challenge to an Oklahoma state ban on April 17 and, separately, a Richmond-based appeals court will in May take up a challenge to a Virginia same-sex marriage ban.
Before the judges on Thursday was a law adopted by Utah voters in 2004, by a 66 to 34 percent margin, defining marriage as only between a man and a woman. Three couples, one gay and two lesbian, challenged the law and all were in the courtroom. They were led by plaintiffs Derek Kitchen and Moudi Sbeity, who were denied a marriage license by the Salt Lake County clerk's office last year.
The Kitchen case begun in March 2013 was among the handful of lawsuits seeking marriage rights pending when the Supreme Court ruled in U.S. v. Windsor. Most of the estimated 50 lawsuits now working their up through the courts were filed after that decision.
The case is Kitchen, et al v. Herbert, et al in the 10th U.S. Circuit Court of Appeals, No. 13-4178