This article is not clear. It references several different issues but does not explain any of them well enough for someone not keeping track of Wyoming's disputes to understand just what the conflict is.
That's a frequent complaint of Casper ST readers, and one that's drawing some interest in the startup of a competing daily newspaper in the region.
The following FReeppost contains the Associated Press report on the matter, as published in the Rocky Mountain News.
It is hopefully more clear for you than the CST piece.
I read another take on this and what the ATF has a problem with Wyomings' definition of "expunged".
Apparently Wyoming does not physicaly destroy the records, and in fact they could be used to increase penalties should the person commit another offense in the future.
AFT is being pretty picky here imo, but then again I'm of the opinion they shouldn't even exist along with junk unconstituional gun laws like the Lautenberg Act.