The Lower Brule Sioux Tribe is a sovereign nation defined by its government-to-government relationship with the United States; as part of the Great Sioux Nation, the Tribe signed treaties in 1824, 1851, 1865 and 1868 with the federal government that constitute the legal documents establishing boundaries and recognizing the rights of sovereign tribal governments.

The Tribe was chartered under the Indian Reorganization Act of June 18, 1934. Its constitution was ratified on July 11, 1936, and bylaws were approved in 1960. The Tribe has contracted several aspects of self-government under the 1975 Indian Self Determination and Education Assistance Act, PL 93-638. On June 17, 1974, the constitution and bylaws were amended, and on September 2, 1986, they were again amended and a code of ethics adopted.

Tribal affairs are conducted by a six-member Tribal Council who are elected to serve two-year terms. Council offices include the chairman, vice-chairman, secretary/treasurer, and three Council members. The Tribal Council Chairman serves as the Chief Executive Officer and Administrative head of the Tribe.

The Chairman, Vice-Chairman, and Secretary-Treasurer, and the three Council Member positions are elected at large.