In Thompson v. United States (1979), the Supreme Court ruled on a case involving the interpretation of a federal statute that imposes enhanced penalties for committing a felony with a firearm. The defendant, Thompson, had been convicted of bank robbery and was found to have carried an unloaded gun during the crime. He argued that because his weapon was not loaded, it did not constitute "use" under the law in question. However, the court disagreed and upheld his conviction and sentence enhancement. The majority opinion held that carrying an unloaded firearm could still intimidate victims or deter resistance during a crime - thus constituting use under this law's definition even if it wasn't fired or shown to anyone else present at the scene of crime. This decision clarified how broadly courts should interpret laws regarding firearms in criminal cases: they are meant to discourage any involvement of guns in illegal activities regardless their operational status.

In the dissenting opinion for Thompson v. United States, Justice William Rehnquist disagreed with the majority's interpretation of Rule 52(b) of the Federal Rules of Criminal Procedure and its application to this case. He argued that a plain error affecting substantial rights should be corrected regardless if it was brought up in trial or not. In his view, Thompson’s conviction on both conspiracy and substantive counts did not constitute double jeopardy as each count required proof of an additional fact which other did not require; thus they were separate offenses under Blockburger test. Furthermore, he contended that even if there had been an error in sentencing, it would have been harmless beyond reasonable doubt since sentences ran concurrently and no greater punishment was imposed than law prescribed for either offense separately.