DENVER — The first ruling by a federal appeals court that states cannot prevent gay couples from marrying makes it more likely the Supreme Court will ultimately have to make a decision it has so far avoided — do states have the ability to prohibit same-sex marriage?

The court danced around that question precisely one year ago when it issued a pair of rulings on gay marriage. At the time, Justices Ruth Bader Ginsburg and Stephen Breyer warned about the high court trying to enforce societal changes through judicial fiat, with Ginsberg citing the lingering abortion rights battle ever since the court legalized the practice in Roe v. Wade.

The high court’s caution was evident in its rulings: It upheld a decision striking down California’s gay marriage ban but relied on technicalities rather than finding a national right for same sex couples to marry. Then it struck down parts of the federal Defense of Marriage Act, finding same-sex marriages from states where the practice was legal must be recognized.

That decision triggered an avalanche of 17 straight court decisions upholding the rights of gays to marry, including Wednesday’s 2-1 ruling from the 10th Circuit Court of Appeals in Denver, the highest court to weigh in since the Supreme Court. Utah, whose gay marriage ban was struck down in the decision, is considering an appeal to the Supreme Court.

“This tees it up for possible Supreme Court review,” said William Eskridge, a law professor at Yale University. “When a federal appeals court strikes down a major state law, there is a lot more pressure for the justices to take that.”

There is no guarantee that the Utah case will be the one that makes it to the top court. Five other appellate courts are considering similar cases, and any of those could be the one taken. The soonest a case could be decided is 2015, but often the Supreme Court waits for a split in appellate courts before considering an issue.

“I don’t know if the Supreme Court is going to wait for a circuit split as long as it usually does,” said Nancy Leong, a law professor at the University of Denver, noting that the recent judicial unanimity on the issue could make that a long wait. Meanwhile, she noted, countless gay couples are eager to marry and less and less willing for the slow pace of the courts.

That was on display in Colorado on Wednesday afternoon, when the county clerk in the liberal city of Boulder announced she would issue same-sex marriage licenses even though the 10th Circuit — which along with Colorado and Utah includes, Kansas, New Mexico, Oklahoma and Wyoming — stayed its decision pending appeal. The state’s attorney general declared the licenses invalid because Colorado’s gay marriage prohibition is still the law, but Clerk and Recorder Hillary Hall said she would continue to issue them until stopped by a court.

Wednesday’s ruling stressed the urgency of overturning gay marriage bans rather than waiting for new laws to be written by elected officials.