25 CFR §900.26

In those situations the Secretary is required, as appropriate, to approve the portion of the program, function, service, or activity that is authorized under section 102(a) of the Act, or approve a level of funding that is authorized under section 106(a) of the Act. As noted in § 900.25, the approval is subject to any alteration in the scope of the proposal that the Secretary and the Indian tribe or tribal organization approve.