Whether the Sioux Reservation was Indian country within the territorial reach of the federal court sitting under federal authority.
Holding
Yes. The reservation was Indian country, and the Dakota territorial district court could exercise federal judicial power there over offenses that Congress had made punishable under federal law.
Reasoning
Although the Revised Statutes no longer contained the 1834 Act's formal definition of Indian country, the Court treated that earlier definition as useful in construing the surviving statutes that continued to refer to Indian country. Under the Court's prior decision in Bates v. Clark, land remained Indian country while Indian title remained unextinguished, absent a contrary treaty or statute.
The Sioux Reservation fell within this understanding of Indian country. It lay geographically within Dakota Territory, even though federal law excluded it from the Territory for purposes of territorial civil government in order to protect tribal rights.
The Dakota district court had two capacities: as a territorial court it enforced local territorial law, and as a court vested by Congress with federal circuit- and district-court jurisdiction it could enforce federal criminal law. Thus, it could hear a federally cognizable offense committed on the reservation—but only if Congress had actually made the conduct a federal offense.