## Facts

- Wyoming conducted a general adjudication of all water rights in the Big Horn River system, including tribal federal reserved rights for the Wind River Indian Reservation and state-law appropriative rights.
- In earlier proceedings, the tribes’ reserved rights were quantified primarily for irrigation purposes with a reservation-date priority.
- After quantification, the tribes adopted a tribal water code, created a tribal water agency, and issued permits for uses including instream flows for fisheries.
- A district court phase decree stated the tribes could change the use of their reserved rights without regard to Wyoming water law.
- The same decree replaced the state engineer with the tribal water agency as administrator for both reserved rights and state-permitted rights within the reservation.
- The State of Wyoming and non-Indian water users appealed these determinations.

## Issues

1. Whether the tribes may change the use of their quantified federal reserved water rights (including to instream flows) without complying with Wyoming change-of-use procedures.
2. Whether a court may substitute a tribal water agency for the state engineer as administrator of all water rights within the reservation, including state-law rights.
3. How federal supremacy of reserved rights interacts with state statutory administration in a comprehensive stream adjudication.

## Decision

- The Wyoming Supreme Court reversed the decree provisions allowing changes of use without regard to Wyoming law.
- The court held changes in use of the tribes’ quantified reserved rights are subject to Wyoming procedural requirements, so long as those procedures do not conflict with federal law or substantially impair the reserved right.
- The court reversed the substitution of the tribal water agency for the state engineer.
- The court held the state engineer remains the primary administrator for water rights in the system, including within the reservation, while administering in a manner consistent with the tribes’ federally protected priority.
- The case was remanded for further proceedings consistent with these rulings.

## Legal Principles

- Federal reserved water rights are federal in origin and enjoy federal supremacy as to existence, priority date, and scope as adjudicated.
- State law may supply administrative and procedural mechanisms (including change-of-use processes) for implementing reserved rights, provided state procedures do not condition, diminish, or defeat the federal right.
- A general adjudication may integrate federal/tribal rights into a unified state-administered system rather than creating parallel, competing administrative regimes.
- State officials may administer priority-based distribution affecting reservation waters if administration respects the quantified tribal reserved rights.

## Conclusion

The court required tribal changes in use of quantified reserved rights to proceed through Wyoming’s change-of-use procedures unless those procedures conflict with federal law or substantially impair the reserved right, and it rejected a decree that displaced the state engineer with a tribal agency as the administrator of all reservation water rights.


In re Gen. Adjudication of All Rights to Use Water in the Big Horn River Sys., 835 P.2d 273 (Wyo. 1992)