For the first time, a federal appeals court has struck down a state's ban on same-sex marriage.
A three-judge panel of the 10th Circuit Court of Appeals in Denver voted 2-1 that Utah's ban is unconstitutional.
"We hold that the Fourteenth Amendment protects the fundamental right to marry, establish a family, raise children, and enjoy the full protection of a state's marital laws. A state may not deny the issuance of a marriage license to two persons, or refuse to recognize their marriage, based solely upon the sex of the persons in the marriage union," the court said.
The Utah attorney general's office said it plans to appeal to the U.S. Supreme Court.
The 10th circuit ruling came on the same day that a federal judge struck down Indiana's ban on same-sex marriage, the latest in a series of lower court rulings that tossed out state prohibitions.
A federal judge in Utah struck down the ban in December and gay couples rushed to tie the knot during a two-week window before the ruling was put on hold pending appeal.
The 10th Circuit ruling is also on hold, pending appeals.
But Amy Fowler, a Utah lawyer who married her partner after the lower court ruling in December, said she was on the verge of tears of happiness after reading the decision.
"It's amazing," she said. "I'm reading the opinion right now and I think we certainly hoped for it and maybe expected it a little bit — but this is incredible.
"We have to wait a little longer to see what happens next but this is a step in the right direction," she added. "We're one step closer to actually being really married. It’s exciting."
Derek Kitchen, one of the plaintiffs that brought the original suit, said he was "overjoyed."
“Since the lawsuit was filed last year, we have received so much support from so many people in our state, and we are now looking forward to the day when we will finally be married,” he said in a statement.
Utah Attorney General Sean Reyes said his lawyers were reviewing the ruling.
"Although the Court’s 2-1 split decision does not favor the State, we are pleased that the ruling has been issued and takes us one step closer to reaching certainty and finality for all Utahns on such an important issue with a decision from the highest court," his office said in a statement.
"For that to happen, the Utah Attorney General's Office intends to file a Petition for Writ of Certiorari to the United States Supreme Court."
John Eastman, chairman of the board of the National Organization for Marriage, which opposes same-sex marriage legalization, said he was disappointed by the 10th Circuit decision but "quite encouraged" by the dissent written by one justice.
Despite the cascade of rulings across the country backing gay marriage, Eastman said he is confident his side will prevail in the nation's highest court.
"All of the lower courts combined don't outweigh a Supreme Court decision," he said.