Long before there was a U.S. Constitution for the American republic, there were treaties among Indian Nations and between Indian Nations and colonial governments reflecting ideals of consultation and negotiation among self-determining peoples. Indigenous traditions of treatymaking were based upon mutual recognition and respect. These traditions of constitutional negotiation have persisted to this day. Despite the absence of formal constitutional entrenchment for their sovereignty in current U.S. law, Indian Nations have maintained traditions of self-governance and continued to negotiate the terms of their association with other peoples. Scholars have argued that Indian treaties and agreements provide constitutional law, or something like it, for governance in Indian Country. Using negotiations between the United States and the states as a point of comparison, this Article works through precisely what it might mean to think about negotiations in Indian Country in constitutional terms. Indian treaties and agreements constitute institutional rules of the game for intergovernmental relationships and express fundamental values about those relationships. In this sense, they help constitute our Tribal republic.