Federalism

Federalism is the constitutional structure under which power is divided between the federal government and the states. Each level has its own authority, officials and laws, and both operate directly on the people. The framers designed it to prevent concentration of power and to let states act as "laboratories of democracy," a phrase from Justice Louis Brandeis.

The Constitution gives the federal government enumerated powers and reserves the rest to the states and the people under the Tenth Amendment, while the Supremacy Clause makes valid federal law supreme. The balance has shifted over time. "Dual federalism" imagined separate spheres, while "cooperative federalism" describes the later pattern of shared programs funded by federal grants and run by states, as in Medicaid. Courts police the line through doctrines like anti-commandeering and limits on the Commerce Clause.

Conservatives often invoke federalism to support state control of education, health care and criminal justice, and to oppose federal mandates. The principle is not tied to either party: liberal states use it to resist federal immigration or drug enforcement, and conservative states use it to resist federal regulation. Critics note that it has also been used to defend slavery and segregation, and that uneven state policies can leave rights unprotected. It is related to subsidiarity.