25 U.S. Code § 122 - Limitation on application of tribal funds
No funds belonging to any Indian tribe with which treaty relations exist shall be applied in any manner not authorized by such treaty, or by express provisions of law; nor shall money appropriated to execute a treaty be transferred or applied to any other purpose, unless expressly authorized by law.
Source(R.S. § 2097.)
R.S. § 2097 derived from act July 26, 1866, ch. 266, § 2,14 Stat. 280.