Whether the Act's instruction that the term destructive device "shall not include any device which is neither designed nor redesigned for use as a weapon" describes an essential feature that the government must prove in order to obtain a conviction under 26 U.S.C. § 5861(d), or instead sets forth an affirmative defense.

Whether the National Firearms Act's language regarding 'destructive device' defines an essential element of the crime or an affirmative defense