Alvarado v. Gonzales, 484 F.3d 535 (8th Cir. April 17, 2007) (per curiam) (federal conviction of possession of firearms and ammunition by an unlawful user of a controlled substance, under 18 U.S.C. 922(g)(3), constituted aggravated felony firearms conviction, for purposes of removal and cancellation of removal, despite the alleged sporting purpose of the guns at issue).