Jeffery T. Ulmer & Mindy S. Bradley have published Punishment in Indian
Country: Ironies of Federal Punishment of Native Americans in Justice Quarterly:

Ulmer Bradley (2018) – Punishment in Indian Country

Here is the abstract:

Native Americans are US citizens, but they are also tribal nationals subject to complex and unique criminal jurisdiction arrangements over Indian lands. Tribal nations typically have tribal court jurisdiction over less serious crimes, but for serious crimes the federal justice system often supersedes tribal authority, exposing Native Americans to more severe punishments. In addition, recent federal programs have attempted to foster greater tribal/federal criminal justice coupling. Yet, examinations of criminal punishment of Native Americans are few, and most are outdated and/or of very limited generalizability. We examine the punishment of Native American defendants in federal court, focusing on 28 federal districts with substantial Indian presence. Using recent US Sentencing Commission data, as well as contextual data from the Bureau of Indian Affairs and tribal courts, we focus on differences in the federal sentencing of Native American defendants, and how these differences are conditioned by indicators of tribal-federal criminal justice coupling.