This chapter turns back to the scope of national powers, and argues that the original meaning of the Commerce Clause limits Congress to regulating the exchange of goods across state lines, and critiques the Supreme Court’s modern, expansive interpretation of the clause. It demonstrates, however, that the national commerce power was understood to be exclusive, lending support to the modern dormant Commerce Clause doctrine that restricts states from interfering with interstate commerce and that many originalists have opposed. It argues that, as originally understood, States retain police powers to regulate the health, safety, morals, and welfare of their populations and can incidentally affect interstate commerce through police regulations, as long as they have a legitimate purpose and do not target interstate commerce. Congress, similarly, could incidentally affect the states’ police powers or private conduct beyond the enumeration of powers so long as it was genuinely exercising its power over interstate commerce, such as when it closed the channels of interstate commerce to goods produced with child labor. This formalist approach reveals a symmetry in the original distribution of power between Congress and the states.