US v. Myers: Myers pleaded guilty to being a felon in possession of a firearm. The firearm at issue was one that had been listed in 18 USC 921(a)(30) as part of the assault weapons ban that lapsed in 2004. Applying the 2006 version of the Sentencing Guidelines (which were in effect at sentencing), the district court enhanced Myers's sentence six levels because the firearm was capable of accepting a large capacity magazine. Myers objected, arguing that the 2005 version of the Guidelines, in effect at the time of the offense, should be used. That version of the Guidelines did not have the large magazine enhancement, but applied a six-level enhancement if the firearm was listed in 921(a)(30). Since that section had lapsed before he committed the offense, Myers argued that the 2005 enhancement was no longer in effect and ex post facto prohibitions applied to prevent his sentence from being enhanced. The district court disagreed.
As did the Fourth Circuit. The court noted that Myers's ex post facto argument only made sense if the lapsing of the assault weapons ban automatically invalidated the 2005 Guideline enhancement provision. But that was not the case, as the Sentencing Commission has the authority to enhance sentences for conduct that is not criminal. Furthermore, the language of the 2005 enhancement only required that a particular weapon be listed in 921(a)(30), not that it be illegal to possess under the assault weapons ban.
In a footnote, the court explained that its resolution of the issue on that ground made it unnecessary to address the Government's argument about the scope of ex post facto protections in a post-Booker world (a topic on which some other courts have split).