In 1990, Congress passed the Gun-Free School Zones Act (GFSZA), making it a federal offense "for any individual knowingly to possess a firearm in a place that the individual knows, or has reasonable cause to believe, is a school zone." Lopez (defendant), a student who brought a gun to his high school, was confronted by school authorities, arrested, and charged with violating the GFSZA. Lopez was tried and convicted. In his appeal, he brought suit against the United States government (plaintiff), challenging the constitutionality of the GFSZA as a regulation based on Congress’s Commerce Clause power. The Court of Appeals for the Fifth Circuit agreed with Lopez and reversed his conviction. The United States petitioned for certiorari to the United States Supreme Court, which granted the petition.