25 U.S.C. § 12
Agent to negotiate commutation of annuities
The Commissioner of Indian Affairs is authorized to send a special Indian Agent, or other representative of his office, to visit any Indian tribe for the purpose of negotiating and entering into a written agreement with such tribe for the commutation of the perpetual annuities due under treaty stipulations, to be subject to the approval of Congress; and the Commissioner of Indian Affairs shall transmit to Congress said agreements with such recommendations as he may deem proper.