McCulloch v. Maryland, 17 U.S. 316 (1819), was a landmark U.S. Supreme Court decision that defined the scope of the U.S. Congress's legislative power and how it relates to the powers of American state legislatures. The dispute in McCulloch involved the legality of the national bank and a tax that the state of Maryland imposed on it. In its ruling, the Supreme Court established firstly that the "Necessary and Proper" Clause of the U.S. Constitution gives the U.S. federal government certain implied powers necessary and proper for the exercise of the powers enumerated explicitly in the Constitution, and secondly that the American federal government is supreme over the states, and so states' ability to interfere with the federal government is restricted. Since the legislature has the authority to tax and spend, the court held that it therefore has authority to establish a national bank, as being "necessary and proper" to that end.

The Supreme Court of the United States (SCOTUS) is the highest court in the federal judiciary of the United States. It has ultimate appellate jurisdiction over all U.S. federal court cases, and over state court cases that turn on questions of U.S. constitutional or federal law. It also has original jurisdiction over a narrow range of cases, specifically "all Cases affecting Ambassadors, other public Ministers and Consuls, and those in which a State shall be Party." The court holds the power of judicial review: the ability to invalidate a statute for violating a provision of the Constitution. It is also able to strike down presidential directives for violating either the Constitution or statutory law.