A grand jury indictment authorized the federal government (plaintiff) to prosecute Pedro Serrano (defendant) for possessing body armor despite being a felon convicted of a crime of violence, in violation of 18 U.S.C. § 931(a). Serrano's state-court conviction for robbery and his alleged possession of a bullet-resistant vest were consistent with the 18 U.S.C. §§ 16 and 921(a)(35) definitions of "crime of violence" and "body armor." Section 921(a)(35) confined its definition of body armor to items of personal protective gear "sold or offered for sale in interstate commerce," but the indictment made no mention of interstate commerce. Serrano moved to dismiss the indictment, contending: (1) that § 931(a) violated the Second Amendment; (2) that as applied to Serrano's case, the statutory terms "crime of violence," "body armor," and "sold or offered for sale" were unconstitutionally vague; (3) that in enacting § 931(a), Congress made no finding strong enough to satisfy the Commerce Clause that there is a nexus between body armor and interstate commerce; and (4) that the indictment failed to allege such a nexus, which is an essential element of a § 931(a) offense.