A system of government in which power is divided between a national (federal) government and various regional governments. As defined by the United States Constitution, federalism is a fundamental aspect of American government, whereby the states are not merely regional representatives of the federal government, but are granted independent powers and responsibilities. With their own legislative branch, executive branch, and judicial branch, states are empowered to pass, enforce, and interpret laws, provided they do not violate the Constitution. This arrangement not only allows state governments to respond directly to the interests of their local populations, but also serves to check the power of the federal government. Whereas the federal government determines foreign policy, with exclusive power to make treaties, declare war, and control imports and exports, the states have exclusive power to ratify the Constitution. Most governmental responsibilities, however, are shared by state and federal governments: both levels are involved in such public policy issues as taxation, business regulation, environmental protection, and civil rights.
Note: The precise extent of state and federal responsibility has always been controversial. Republican administrations, for example, have tended to grant more authority to the states, thereby encouraging political and economic freedom but discouraging comprehensive social welfare. Until the middle of the twentieth century, the Supreme Court left the interpretation of many civil rights guarantees to the states, resulting in widespread discrimination against minorities.