The Supreme Court's decisions in Turner v. United States and ., firmly established the doctrine of tribal sovereign immunity. A Native American tribe enjoys sovereign immunity from suit, unless "Congress has authorized the suit of the tribe has waived its immunity." Any such waiver must be clear and unequivocal to be effective. Furthermore, "[c]ourts construe waivers of a tribe's sovereign immunity strictly and hold a strong presumption against them."
Devin Ryan, Off the Reservation: Native American Tribes Reasserting Sovereign Immunity to Trump Arbitration Agreements, 4 286 (2012).