While most people know that convicted felons may be prevented from owning firearms, there is a federal law that prohibits those convicted of misdemeanor domestic abuse from owning them as well.
And although it's a federal law, it applies to State misdemeanors — "convictions in any court" — because guns move about in interstate commerce, and Congress may regulate that.*
There is an exception to the federal law, however, in that those convicted of misdemeanor domestic abuse whose conviction has been "expunged or set aside" may once again own firearms.
For some reason, in 2004, the Wyoming legislature put in place a procedure by which the individuals in question could apply to have their convictions "expunged or set aside," but only for the narrow, specific purpose of "restoring any firearms rights lost."
In other words, a conviction still stood as a prior offense, for example, if the individual was again convicted of misdemeanor domestic abuse, but not if they wanted to own a firearm. And, presumably, since an element of misdemeanor domestic abuse in Wyoming is "an attempted use of physical force," that subsequent offense might involve a newly restored firearm under Wyoming law.
Furthermore, the Wyoming statute would have had the effect of allowing convicted domestic abusers to secure a concealed carry permit and thus be exempt from federal background checks, which would otherwise uncover the still existing domestic abuse conviction.
The federal Bureau of Alcohol, Tobacco, Firearms and Explosives objected because, the Bureau argued, what Congress meant by "expunged or set aside" was completely expunged or set aside, not simply a State setting aside those particular effects of the conviction that prevented the individual from owning a firearm.
Wyoming challenged the Bureau's interpretation in federal district court, and its challenge was dismissed. The State then appealed and yesterday the 10th Circuit affirmed the district court, holding that while the terms "expunge" and "set aside" may have different meanings in Wyoming caselaw and indeed, meanings different from each other, what Congress meant by both is the same thing.
That is, the very fact and existence of the conviction itself needs to have been erased from the record in order to qualify for the federal exception, not just one of its effects, that of its prohibiting firearm ownership to convicted domestic abusers.
This seems to me a strange attempt by Wyoming lawmakers, and there is considerable irony in the argument of the State's Attorney General, Patrick J. Crank, that it was the ATF's interpretation of federal law which was "arbitrary and capricious."
Wyoming v. United States (.pdf, 25 pgs.)
* And yes, I'm aware that this is arguably a non sequitur, but the constitutionality of the federal law wasn't at issue here.