In Staples v. United States, 114 S. Ct. 1793, 1804 (1994), the Supreme Court ruled that, to obtain a conviction for an unregistered automatic weapon, in violation of the National Firearms Act (NFA) (26 U.S.C. § 5861(d)), the government must prove that the defendant knew of the features or characteristics of the weapon that brought it within the scope of the criminal proscription. In the wake of the Staples decision, the Solicitor General's Office has concluded that the government should take the position that in all cases prosecuted under the NFA, the government must prove that the defendant knew the features of the firearm that brought it within the scope of the Act. The Criminal Division has issued a memorandum to all United States Attorneys explaining this policy, and has provided suggested jury instructions regarding the knowledge element of a violation of the NFA.

In addition to NFA violations, the Criminal Division believes that the same scienter standard should apply to 18 U.S.C. § 922(o), which makes it unlawful to transfer or possess a machinegun. In such cases, prosecutors should anticipate the requirement that they must prove the defendant's knowledge that the firearm at issue was a machinegun, and they should accede to defense requests for an instruction requiring a finding of such knowledge.