(1) There is hereby exempted from the taxes imposed by this chapter sales occurring within the boundaries of an Indian reservation located in Idaho when the business or enterprise is wholly owned and operated by an Idaho Indian tribe identified in section 67-4001, Idaho Code.
(2)  As used in this section the word "reservation" means lands which are:
(a)  Indian lands federally declared to be reservations because they are reserved for Indian tribes by treaty between Indian tribes and any territorial governments, state government, or the United States Government; or, established by acts of the United States congress; or established by formal decision of the executive branch of the United States; or
(b)  Held by an Idaho Indian tribe not holding lands which meet the definition of subsection (2)(a) of this section and are tribal lands held in trust by the United States for the use and benefit of such tribe but not placed in trust after the effective date of this act.