The 10th Circuit Court of Appeals has struck down Utah's ban on same sex marriage in a 2-1 decision. The decision has been stayed pending appeal. It could be reversed either by the judges of the 10th Circuit sitting en banc, or by the U.S. Supreme Court if it chose to grant certiorari.
This follows a long and uninterrupted string of decisions by courts in other jurisdictions, most recently the Indiana Supreme Court, to the same effect. But, this is the first federal appellate court ruling finding a same sex marriage ban to be unconstitutional. (Incidentally, West Virginia also ceased to recognize the tort of criminal conversion this week, decades after rejecting the tort of alienation of affections.)
Colorado, which also bans same sex marriage, is also in the 10th Circuit. Colorado does not necessarily present the same issues, because unlike Utah, it has civil unions that provide all rights except the name "marriage" to same sex couples under state law. The status of a civil union in Colorado for federal law purposes is less clear, and many couples in civil unions in Colorado have legally married in another state to assure federal recognition of their marriage.
But, the tenor of the majority opinion in the case suggests that its reasoning is applicable broadly enough to extend to Colorado, particularly if one concludes that a Colorado civil union does not confer marriage treatment under federal law.
This ruling surely presages the likely result in an Oklahoma case pending in the same court before the same panel of judges on the same issue, since Oklahoma, unlike Colorado, does not have marriage-like rights for same sex couples in civil unions, unless this decision is overruled by an en banc 10th Circuit or the U.S. Supreme Court in the meantime. Oral argument in the two cases was held on the same day before the same judges.
The Boulder County Clerk and Recorder has begun to issue same sex marriage licenses in response to the ruling, over the objections of the Colorado Attorney General, reasoning that the opinion is controlling 10th Circuit law and that the stay applies only to Utah. I'm not terribly impressed with that reasoning (the stay is of the overall decision pending appeal and is not really limited to Utah in the sense argued), but the grassroots action by a local elected official is a typical posture for same sex marriage litigation in many states.
The U.S. Supreme Court rejected the federal portion of the Defense of Marriage Act ruling that determining who may be married is derivative of state law absent a good reason otherwise, but left the full faith and credit provisions that allow states to refuse to recognize same sex marriages from other states in tact.
So far, it has not accepted any cases resolving the constitutionality of same sex marriage bans at the state level. It could quite plausibly refrain from doing so until a circuit split evolves (if one does). It could have ruled in cases holding that same sex marriage bans are illegal from state supreme courts, but those rulings often incorporate state as well as federal constitutional rights. In contrast, this ruling if the first decision finding same sex marriage bans unconstitutional that is decided solely under federal law in a federal court that is ready for U.S. Supreme Court review.