The U.S. Constitution establishes a system of dual sovereignty between the states and the federal government, with each state having its own government, endowed with all the functions essential to separate and independent existence. Although the Supremacy Clause of the Constitution designates “the Laws of the United States” as “the supreme Law of the Land,” other provisions of the Constitution—as well as legal principles undergirding those provisions—nonetheless prohibit the national government from enacting certain types of laws that impinge upon state sovereignty. The various principles that delineate the proper boundaries between the powers of the federal and state governments are collectively known as “federalism.”
In addition to the internal constraints on Congress’s authority, the Constitution also imposes external limitations on Congress’s powers vis-à-vis the states—that is, affirmative prohibitions on certain types of federal actions found elsewhere in the text or structure of the Constitution. The Supreme Court has recognized, for instance, that the national government may not commandeer the states’ authority for its own purposes by forcing a state’s legislature or executive to implement federal commands. Nor may Congress apply undue pr
essure to coerce states into taking actions they are otherwise disinclined to take. Furthermore, the principle of state sovereign immunity—which limits the circumstances in which a state may be forced to defend itself against a lawsuit against its will—imposes significant constraints on Congress’s ability to subject states to suit. Finally, the Supreme Court has recognized limits to the extent to which Congress may subject some states to more onerous regulatory burdens than other states.