In McClanahan v. Arizona State Tax Comm'n (1973) 411 U.S. 164, the court was required "to reconcile the plenary power of the States over residents within their borders with the semi-autonomous status of Indians living on tribal reservations." (McClanahan, supra, 411 U.S. at p. 165.) McClanahan involved an attempt by the state of Arizona to impose an income tax on an enrolled member of the Navajo tribe who both lived on, and earned her income from sources within, the Navajo reservation in Arizona. (Id. at pp. 165-166.) The court, synopsizing the question it was confronting, stated: "It may be helpful to begin our discussion of the law applicable to this complex area with a brief statement of what this case does not involve. We are not here dealing with Indians who have left or never inhabited reservations set aside for their exclusive use or who do not possess the usual accoutrements of tribal self-government. Nor are we concerned with exertions of state sovereignty over non-Indians who undertake activity on Indian reservations. Nor, finally, is this a case where the State seeks to reach activity undertaken by reservation Indians on nonreservation lands. Rather, this case involves the narrow quest- ion whether the State may tax a reservation Indian for income earned exclusively on the reservation." (Id. at pp. 167-168.) After surveying the development of American Indian law from its earliest origins, McClanahan concluded that the analysis of whether a state may assert jurisdiction over Indians has shifted from concepts of inherent Indian sovereignty toward federal preemption principles (McClanahan, supra, 411 U.S. at p. 172 "the modern cases thus tend to avoid reliance on platonic notions of Indian sovereignty and to look instead to the applicable treaties and statutes which define the limits of state power"), although the court cautioned the Indian sovereignty doctrine remained relevant "not because it provides a definitive resolution of the issues in this suit, but because it provides a backdrop against which the applicable treaties and federal statutes must be read." (Ibid.) McClanahan then observed that considering the 1868 treaty between the Navajo Nation and the United States government, "it cannot be doubted that the reservation of certain lands for the exclusive use and occupancy of the Navajos and the exclusion of non-Navajos from the prescribed area was meant to establish the lands as within the exclusive sovereignty of the Navajos under general federal supervision." (Id. at pp. 174-175.) The Court further stated that "since the signing of the Navajo treaty, Congress has consistently acted upon the assumption that the States lacked jurisdiction over Navajos living on the reservation" (id. at p. 175), and noted provisions in both the Arizona Enabling Act (36 Stat. 557) and the Buck Act (4 U.S.C. 105-110) contained language implying the income of a Navajo living on and derived from the Navajo reservation was exempt from state income taxation (411 U.S. at pp. 175-176).