U.S. Constitutional law
Constitutional law, U.S., section of the law that interprets and enforces the provisions of the U.S. Constitution. Although the Constitution, with its 7,000 words, launched the fledgling Union as a sovereign, democratic nation, it refrained from specifying too precisely the limits of governmental power or the roles of its institutions. A closer definition of these was left to history and experience. Constitutional law studies this historical development and pronounces on the contemporary status of its many concepts, concentrating on 3 topics: judicial review, the separation of powers, and the federal system. Judicial review deals with the powers of the U.S. courts—ultimately the Supreme Court—to pass judgment on the constitutionality of laws or specific acts of government. The U.S. Constitution did not provide for judicial review, but the Supreme Court has claimed, and exercised, the right to decide on constitutionality ever since Chief Justice John Marshall's famous decision in Marbury v. Madison (1803). His reasoning was simple: The Constitution is the supreme law of the land and it is the function of the courts to uphold the law; consequently, the courts are duty-bound to declare invalid any government law or action in conflict with the basic provisions of the Constitution. The Supreme Court exercises its power of review with restraint, and the burden of proof rests on the party challenging the law's constitutionality, not on the legislation. The Court assumes that the legislation does not enact measures intended to violate the Constitution.
The doctrine of separation of powers maintains that despotism is best prevented by dividing the powers of government among several branches that “check and balance” one another. The Constitution confers the legislative power upon Congress, the judicial authority upon the courts, and executive power upon the president. The federal system divides the powers of government between the national, or federal, government and the state administrators. The powers of the national government are enumerated in the Constitution, all other powers being reserved to the state governments. However, provisions like the clause that gives Congress the power to make all laws “necessary and proper” to carry out its Constitutional function and the right to regulate interstate commerce have greatly increased federal power.