American Indian tribal power has typically expanded since the 1960s. During this period, often referred to as the Self-Determination Era, tribes have regained much of their earlier political centrality. One rarely addressed limitation during this period is the inability of tribal polities to break into smaller units while maintaining recognition as legitimate. This essay identifies the inability of tribes to exercise what the authors call compositional flexibility and fracture to form new polities discrete of the previous tribe. The authors argue the absence of compositional flexibility shapes tribal politics and is at odds with many forms of traditional governance systems.