Enumerated and Implied Powers

The federal government has only the powers the Constitution grants it. Article I, Section 8 lists Congress's powers, including taxing and spending, borrowing, regulating commerce with foreign nations, among the states, and with Indian tribes, coining money, establishing post offices, raising armies, and declaring war. The Tenth Amendment confirms that powers not delegated to the United States are reserved to the states or the people. This structure, limited and enumerated federal power, is the constitutional basis for limited government.

The list ends with the Necessary and Proper Clause, giving Congress power to make all laws necessary and proper for carrying out its enumerated powers. In McCulloch v. Maryland in 1819, Chief Justice John Marshall read the clause broadly to uphold a national bank, a power nowhere listed, establishing the doctrine of implied powers: if the end is legitimate and within the Constitution's scope, Congress may choose any appropriate means not prohibited. Alexander Hamilton had argued the same position against Thomas Jefferson in 1791.

The Commerce Clause has carried most of federal power's growth. In Wickard v. Filburn in 1942 the Court upheld federal limits even on wheat grown for a farmer's own use, because such activity in aggregate affects interstate commerce. Since the 1990s the Court has drawn some lines, striking down a federal ban on guns near schools in United States v. Lopez in 1995 and holding in NFIB v. Sebelius in 2012 that the commerce power could not compel people to buy health insurance, though the mandate survived as a tax. The spending power lets Congress attach conditions to federal grants, within limits the Court set in South Dakota v. Dole in 1987.