The Supreme Court says Wyoming is not taking too much water from a river system it shares with Montana.
The high court on Monday turned away Montana's complaint that Wyoming is taking too much water from the Tongue and Powder rivers in violation of a 1950 agreement between the states.
Montana claimed that more efficient irrigation in Wyoming is preventing runoff from rejoining the river and flowing downstream.
Justice Clarence Thomas wrote the 7-1 decision, which says more efficient irrigation is permissible to the detriment of downstream users. Justice Antonin Scalia was the only dissenting vote.
Justice Elena Kagan did not participate in the case because she worked on it while in the solicitor general's office.