U.S. constitutional law

United States constitutional law is the body of law governing the interpretation and implementation of the United States Constitution.

United States constitutional law defines the scope and application of the terms of the Constitution. It covers areas of law such as the relationship between the federal government and state governments, the rights of individuals, and other fundamental aspects of the application of government authority in the United States. It is a field of law that is broad and complex. Some constitutional scholars maintain that the authors of the Constitution intended that it be vague and subject to interpretation so that it could be adapted to the needs of a changing society. Others maintain that the provisions of the Constitution should be strictly construed and their provisions applied in a very literal manner.

Early in its history, in Marbury v. Madison, 5 U.S. 137 (1803) and Fletcher v. Peck, 10 U.S. 87 (1810), the Supreme Court of the United States declared that the judicial power granted to it by Article III of the United States Constitution included the power of judicial review, to consider challenges to the constitutionality of a State or Federal law. According to this jurisprudence, when the Court measures a law against the Constitution and finds the law wanting, the Court is empowered and indeed obligated to strike down that law. In this role, for example, the Court has struck down state laws for failing to conform to the Contract Clause (see, e.g., Dartmouth College v. Woodward) or the Equal Protection Clause (see, e.g., Brown v. Board of Education), and it has invalidated federal laws for failing to arise under the Commerce Clause of the Constitution (see, e.g., United States v. Lopez).

The Supreme Court's interpretations of constitutional law are binding on the legislative and executive branches of the federal government, on the lower courts in the federal system, and on all state courts. This system of binding interpretations or precedents evolved from the common law system (called "stare decisis"), where courts are bound by their own prior decisions and by the decisions of higher courts. While neither English common law courts nor continental civil law courts generally had the power to declare legislation unconstitutional (only the power to change law), the United States Supreme Court has long been understood to have the power to declare federal or state legislation unconstitutional.

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