Article one, Section 8 of the United States Constitution refers to the power of Congress to regulate commerce with Indian tribes: Congress shall have the power “To regulate Commerce with foreign Nations, and among the several States, and with the Indian Tribes.” That Section was later was interpreted by the United States Supreme Court to mean that Congress has exclusive rights and powers to regulate affairs and trade with Indian tribes. The power that Congress has over Indian tribes is very broad, and is often referred to as ‘plenary power,’ meaning complete. It can limit, modify, or eliminate powers that tribes possess. Congress can even terminate tribal status. The plenary power of Congress is so great that it essentially keeps the states out of Indian affairs.
Congress exercised its power over Indians early on by enacting several statutes. Congress placed Indian affairs under a new Department of War, set aside money to negotiate Indian treaties and appointed federal commissioners to negotiate them. Congress passed a series of laws regulating commerce between Indians and non-Indians beginning with a law which prohibited states and individuals from buying Indian lands (Indian Non-Intercourse Act, 1790). Congress extended the federal jurisdiction over general crimes when non-Indians were involved into the Indian country (General Crimes Act). These early laws of Congress are still in effect today.