(a) The Secretary shall, by regulation, establish reasonable standards for the approval of tribal payments pursuant to section 117a of this title and, where approval is given under such regulations, the United States shall not be liable with respect to any distribution of funds by a tribe under sections 117a to 117c of this title.

(b) Nothing in sections 117a to 117c of this title shall otherwise absolve the United States from any other responsibility to the Indians, including those which derive from the trust relationship and from any treaties, Executive orders, or agreements between the United States and any Indian tribe.