Petitioner's conviction for possession of a firearm by a convicted felon is vacated and remanded, with instructions for the district court to grant his habeas corpus petition, where: 1) United States v. Simmons, 649 F.3d 237 (4th Cir. 2011) announced a new substantive rule that is retroactive on collateral review; and 2) Simmons established that the federal statute under which defendant was convicted does not reach defendants whose prior convictions could not have resulted in a sentence of more than one year in prison.