Quick search by citation:

25 U.S. Code § 25a - Application of civil service laws

The position of Superintendent of the Five Civilized Tribes is included within the competitive classified civil service and shall be subject to civil service laws and rules.

(Mar. 4, 1929, ch. 705, 45 Stat. 1583.)
Executive Documents
Transfer of Functions

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.