How does federalism divide authority between national and state governments?

Federalism divides authority by establishing a system of shared sovereignty between a central national government and intermediate subnational entities, such as states or provinces. Unlike unitary systems, where local powers are devolved at the discretion of the central authority, federal systems provide these intermediate governments with constitutionally protected sovereignty.1

In this structure, a rigid, written constitution serves as the foundation for the division of power. The national government is granted specific, enumerated powers—such as conducting foreign relations, declaring war, and regulating interstate commerce—along with implied powers necessary to implement those functions. Conversely, all powers not delegated to the national government nor prohibited to the states are reserved to the states or the people. These are known as residual or reserved powers, which allow states to maintain their own laws and policies on matters like education, property, and criminal law.1234

This territorial separation of powers acts as a restraint on central authority, safeguarding local liberties and allowing states to function as laboratories for policy experimentation. Disputes regarding the exact boundaries of this authority are common and are typically resolved through judicial review or intergovernmental negotiation.513