The restricted allotment of any Indian may be leased for farming and grazing purposes by the allottee or his heirs, subject only to the approval of the superintendent or other officer in charge of the reservation where the land is located, under such rules and regulations as the Secretary of the Interior may prescribe: Provided, That this provision shall not apply to the Five Civilized Tribes.
25 U.S. Code § 393 - Leases of restricted allotments
For transfer of functions of other officers, employees, and agencies of Department of the Interior, with certain exceptions, to Secretary of the Interior, with power to delegate, see Reorg. Plan No. 3 of 1950, §§ 1, 2, eff. May 24, 1950, 15 F.R. 3174, 64 Stat. 1262, set out in the Appendix to Title 5, Government Organization and Employees.