(a) In general

There are authorized to be appropriated such sums as may be necessary to carry out this subchapter.

(b) Availability of appropriations

Notwithstanding any other provision of this chapter, the provision of funds under this chapter shall be subject to the availability of appropriations and the Secretary is not required to reduce funding for programs, projects, or activities serving a tribe in order to make funds available to another tribe or tribal organization under this chapter.