In the case of United States v. John Bass in 2001, the Supreme Court ruled that under federal law, prosecutors must prove beyond a reasonable doubt that an individual knew they were dealing with a firearm during their crime to convict them for using or carrying it. The defendant, John Bass was convicted by lower courts for drug trafficking and using firearms during his crimes based on evidence from an accomplice who testified he had seen guns at Bass's house. However, no physical evidence linked any specific gun to him nor did it show he used or carried one while committing his crimes. In its decision, the Supreme Court emphasized that mere possession of a firearm is not enough; there must be active use or carriage during criminal activity as per Federal statute 18 U.S.C §924(c). This ruling set important precedent regarding burden of proof in cases involving firearms charges connected to other offenses.

In the dissenting opinion for United States v. John Bass, Justice Thomas disagreed with the majority's interpretation of 18 U.S.C § 924(e). He argued that the statute does not require proof that a defendant knew his possession of firearms was in relation to drug trafficking crimes. Instead, he believed it only requires evidence showing such connection existed. The justice also criticized the majority for creating an unnecessary rule about knowledge requirement which is absent from statutory text and inconsistent with precedent cases like Staples v. United States and Bryan v. United States where knowledge requirements were explicitly stated by Congress in statutes but not inferred by courts when absent.