Congress enacted the Brady Handgun Violence Prevention Act (Brady Act) in 1993 as an amendment to its Gun Control Act of 1968. The Brady Act was a federal gun-control provision that required the United States attorney general to implement a nationwide handgun background check system. While moving towards a national system, in the interim, state and local officials were required to conduct background checks of prospective firearm purchasers. Under the Brady Act, sellers of firearms would report sales to their county Chief Law Enforcement Officers (CLEOs). The CLEOs would then conduct background checks and confirm the lawfulness of the sales. Printz and Mack (plaintiffs) were CLEOs in Montana and Arizona, respectively. Printz brought suit in federal district court against the United States government alleging that the Brady Act was an unconstitutional exercise of Congressional power because it compelled state officers to participate in federal service. The district court held that the provision of the Brady Act requiring CLEOs to perform background checks was unconstitutional, but held that this provision could be separated from the rest of the act, leaving a constitutional, voluntary background check system in place. The Court of Appeals for the Ninth Circuit reversed, holding that none of the Brady Act’s interim provisions were constitutional. The Supreme Court granted certiorari.