Tarrant Regional Water District v. Herrmann, et al., 133 S. Ct. 2120 (U.S. Sup. Ct.. 2013)

(Red River Interstate Water Compact allocates water in Red River which divides Oklahoma and Texas which gives signatory states (AR, LA, OK, TX) "equal rights" to excess water in a sub-basin of river with no state entitled to more than 25 percent of excess water no matter where located; TX argued it was entitled to withdraw water from any part of the river including a tributary to take up to 25 percent, including sub-basin within OK and that Compact preempted OK state water law; court disagreed with TX position; TX cannot take water located in OK without OK's permission; OK state law which regulated out-of-state water users not pre-empted by Compact).