Cato’s brief, joined by the Competitive Enterprise Institute and the National Smokers Alliance, argues that the settlement made by the major tobacco companies, outlined in the Master Settlement Agreement (MSA), constitutes a massive conspiracy in restraint of trade in violation of the Sherman Antitrust Act. Neither Parker nor Noerr-Pennington immunity immunize private parties engaging in state action that itself is illegal and beyond the state’s sovereign powers. Moreover, the scope of the MSA exceeds the federal government’s ability to regulate interstate commerce.