Summary of the case -
The 1974 Boldt Decision affirmed the right for tribes to fish in their usual and accustomed places, and specifically in off-reservation locations. State intervention on fishing rights was limited to very special cases or conservation reasons. Pursuing this decision and case was spurred by the Puyallup River fishing protest in the 1960s. 
Established in 1989, the Centennial Accord affirms a government relationship between the federally recognized tribes of Washington state and the State of Washington. The affirmation of this relationship aspires to improve services to Indian and non-Indian people alike. 
The Dawes Act, or General Allotment Act of 1887 divided reservation land among individuals of the a Tribe, instead of allowing the reservation to manage it as collectively run reservation property. "The remaining land would be opened to white settlement. This resulted in the loss of millions of acres of Indian land."  This allocation and subdivision of reservation land resulted in major loss of land to Native Americans as "Reservation land not allotted to individual Indians [was] declared surplus and offered for sale." 
American Indians gained citizenship and the right to vote after the 1924 Indian Citizenship Act.
The Indian Reorganization Act (Wheeler-Howard Act) was passed in 1934 and established governmental structures used by tribes today. "Tribal courts, funds for higher education, tribal council systems and others evolved out of the IRA. It is said to be the most far reaching piece of Indian legislation to impact Native people in contemporary times, and served as the beginnings of Indian self-determination." 
Sovereignty is defined both as "respect of power, domination, or rank; supreme dominion, authority, or rule" as well as "existing as an independent state." Tribal sovereignty "guarantees a nation the right to govern its own affairs and establish its own laws." The U.S. Constitution recognizes the self-government of tribal nations and their right to do so.