Statutory term that includes all lands within an Indian reservation, dependent Indian communities, and Indian trust allotments (18 U.S.C. § 1151). Courts interpret section 1151 to include all lands held in trust for tribes or their members. See United States v. Roberts, 185 F.3d 1125 (10th Cir. 1999). Tribal authority to imprison American Indian offenders is limited to one year per offense by statute (25 U.S.C. § 1302), a $5,000 fine, or both.