Supreme Court of the United States
Montana v. Wyoming
May 2, 2011563 U.S. 368
Summary
The Court held that the Yellowstone River Compact does not prohibit Wyoming from allowing pre-1950 water appropriators to improve irrigation efficiency, even if this increases consumption and reduces return flows to Montana. The opinion interprets Article V(A) as protecting appropriative rights under state law doctrines of recapture and the no-injury rule, neither of which forbids efficiency improvements. Justice Kagan took no part. Justice Scalia dissented, arguing the Compact’s use of “depleted” limits claims to net consumption.