The Nonintercourse Act is the collective name given to six statutes passed by the United States Congress in 1790, 1793, 1796, 1799, 1802, and 1834 to set boundaries of American Indian reservations. The various acts were also intended to regulate commerce between White Americans and citizens of Indigenous nations. The most notable provisions of the act regulate the inalienability of aboriginal title in the United States, a continuing source of litigation for almost 200 years. The prohibition on purchases of Indian lands without the approval of the federal government has its origins in the Royal Proclamation of 1763 and the Confederation Congress Proclamation of 1783.

An American Indian reservation is an area of land held and governed by a U.S. federal government-recognized Native American tribal nation, whose government is autonomous, subject to regulations passed by the United States Congress and administered by the United States Bureau of Indian Affairs, and not to the U.S. state government in which it is located. Some of the country's 574 federally recognized tribes govern more than one of the 326 Indian reservations in the United States, while some share reservations, and others have no reservation at all. Historical piecemeal land allocations under the Dawes Act facilitated sales to non–Native Americans, resulting in some reservations becoming severely fragmented, with pieces of tribal and privately held land being treated as separate enclaves. This jumble of private and public real estate creates significant administrative, political, and legal difficulties.