It shall be the duty of the Secretary of the Interior, and the officers charged by law with the distribution of supplies to the Indians, under appropriations made by law, to distribute them and pay them out to the Indians entitled to them, in such proper proportions as that the amount of appropriation made for the current year shall not be expended before the end of such current year, so as to prevent deficiencies; and no expenditure shall be made or liability incurred on the part of the Government on account of the Indian Service for any fiscal year (unless in compliance with existing law) beyond the amount of money previously appropriated for said service during such year.
25 U.S. Code § 135 - Supplies distributed so as to prevent deficiencies
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.