"The state has failed to show any legitimate reason, actually any reason at all, for not treating a female spouse in a same-sex marriage the same as a male spouse in an opposite-sex marriage," Benson said in a ruling from the bench.
Utah Attorney General spokeswoman Missy Larsen on Monday confirmed the state's decision not to challenge Benson's finding to the 10th Circuit Court of Appeals in Denver.
Larsen said she could not provide any details about the rationale for the decision, as the state's Solicitor General, Parker Douglas, who argued the case, was out of town.
The Roes, of West Jordan, married Dec. 20, 2013 and welcomed baby Lucy into their family in February. Lucy is the biological child of Kami and was conceived with the help of donated sperm. A hospital refused to issue the couple a birth certificate and said state law required they go though a second-parent adoption process to get one.
Utah had argued that state laws governing assisted reproduction were in place to ensure good statistical data is gathered for vital records and to create greater family stability for children.
Benson's decision, which does not affect gay men who conceive a biological child with help of a surrogate, requires the state to issue the Roes a birth certificate as quickly as possible.
"We're prepared to immediately issue the amended birth certificate once the [judge's ]order is filed," health department spokesman Tom Hudachko said. "As of earlier [Monday] that had not happened yet."
Attorneys for the American Civil Liberties Union, who sued on the Roes behalf, said the ruling is the first in the wake of a June U.S. Supreme Court decision legalizing same-sex unions in all 50 states and sets a precedent for similar parental rights cases nationwide.
On Monday, Utah ACLU spokesman John Mejia said he was pleased the attorney general's office has decided against an appeal.
"We are thrilled for our clients, who have some additional clarity and can continue to move forward with their lives together as a family," he said.