The Commerce Clause

Under the Articles of Confederation, states imposed tariffs and restrictions on each other's goods, and the Constitution responded by giving Congress, in Article I, Section 8, Clause 3, the power to regulate commerce with foreign nations, and among the several states, and with the Indian tribes. In Gibbons v. Ogden, decided March 2, 1824, Chief Justice John Marshall read the power broadly to include navigation and all commercial intercourse that concerns more than one state, striking down a New York steamboat monopoly.

For decades the Court distinguished commerce from manufacturing and agriculture and struck down some New Deal laws, but beginning in 1937 it upheld broad federal regulation. In Wickard v. Filburn in 1942, it held that Congress could limit wheat a farmer grew for his own use because such activity, in the aggregate, substantially affected interstate commerce. The commerce power became the foundation for federal labor, environmental, drug, and civil rights laws, and in Heart of Atlanta Motel v. United States in 1964 the Court upheld the Civil Rights Act's ban on discrimination in public accommodations.

In United States v. Lopez in 1995, the Court struck down a federal ban on guns near schools as unrelated to economic activity, the first such limit in nearly 60 years, and in NFIB v. Sebelius in 2012 it held that Congress could not compel people to buy health insurance under the commerce power. The clause also implies a dormant limit that bars states from discriminating against interstate commerce, and its foreign commerce power underlies tariffs. Supporters of broad readings say a national economy needs national rules, while critics say the commerce power has been stretched to cover almost anything.