The three-judge panel in Denver found it "wholly illogical to believe that state recognition of the love and commitment between same-sex couples will alter the most intimate and personal decisions of opposite-sex couples."
The decision upheld a lower court ruling that struck down Utah's gay marriage ban. However, the 10th US Circuit Court of Appeals panel immediately put the ruling on hold so it could be appealed, either to the entire 10th Circuit or directly to the nation's highest court.
The decision gives increased momentum to a legal cause that already compiled an impressive winning streak in the lower courts after the Supreme Court last year struck down the federal Defense of Marriage Act. Since then, 16 federal judges have issued rulings siding with gay marriage advocates.
The latest of those rulings was in Indiana, where a federal judge on Wednesday struck down that state's same-sex marriage ban in a ruling that immediately allows gay couples to wed. The Indiana attorney general's office said it will appeal.
Now same-sex marriage is legal in 19 states and the Washington capital district in the United States.