Native Americans
Article I, Section 8 of the United States Constitution grants Congress (among other items) the right "To regulate Commerce with foreign Nations, and among the several States, and with the Indian Tribes;"

From 1830 to 1890, the federal government systematically pushed Native Americans from their lands onto government reservations west of the Mississippi River. In 1832, this policy was supported by President, even though the Supreme Court in Worcester v. Georgia directed the state of Georgia to stop forcibly removing native Americans.  At this time, white settlers began pushing into the Great Plains.  Soldiers tried to keep travel routes open for the migrating settlers, and often battled the Native Americans for control of those areas. As noted above, fighting between U.S. Army troops and Indians continued throughout the 1860s and 1870s.

The Homestead Act of 1862 promised to give 160 acres of federally-owned land to settlers for free  if they could farm it for five years.  This encouraged thousands of settlers to move into formally Indian-controlled lands, displacing the natives, and further straining relations with Native Americans.  When the first trans-continental railroad was completed in 1869, native lands seemed even more desirable, and movement westward increased.

By 1871, Native Americans had been made "wards of the state" by the federal government.  They could no longer make individual treaties with the federal government, and most lived on federal reservations.  The Dawes Act of 1887 tried to "Americanize" Indians by abolishing all tribes, and giving former members 160-acre farms (on the reservation) that they would own outright after 25 years. 

The Dawes Act , and others like it, were supposed to provide a road to American citizenship, but more often destroyed native cultures.  It was not until 1924 that all Native Americans were made legal citizens of the Unites States.  It was only in 1934 that natives were given legal right to sovereignty, the right to self-rule, on the reservations.