DeCoteau v. District County Court for the Tenth Judicial District

Background

Two consolidated cases involved members of the Sisseton‑Wahpeton Tribe and whether South Dakota courts could act on events that took place on lands inside the 1867 Lake Traverse reservation but owned and settled by non‑Indians after an 1891 federal law. The 1867 reservation covered about 918,000 acres, with roughly 3,000 tribal members and 30,000 non‑Indians living there. About 15% of the land remained as Indian trust allotments scattered through the area; the rest was bought by non‑Indians after the 1891 Act.

Reasoning

The Court examined the 1889 agreement and the Act of March 3, 1891, which paid the tribe a sum certain ($2.50 per acre) for the unallotted lands and directed those lands be opened to settlement. The majority concluded that Congress and the tribe clearly intended an outright cession of the unallotted lands and that the statute and legislative history show the reservation was terminated. Because the unallotted lands were returned to the public domain, state courts may exercise civil and criminal jurisdiction there; only the retained Indian allotments remain under tribal or federal authority.

Real world impact

Practically, the decision gives state courts authority over conduct on non‑Indian parcels within the former reservation boundaries, while tribal and federal jurisdiction continues only on trust allotments. The opinion noted long historical disagreements among courts and agencies, and the ruling resolves those conflicts by relying on the text and history of the 1891 statute.

Dissents or concurrances

A dissent argued the 1891 Act did not clearly revoke reservation boundaries, warned that splitting jurisdiction into a checkerboard would harm tribal self‑government, and stressed the tribe’s continuing institutions and services across the original reservation.