Wyo. Stat. § 41-4-103
The state engineer is hereby authorized and empowered to receive and grant applications to appropriate water from streams in Wyoming where such water is to be conveyed and used for beneficial purposes within the state of Utah, and the board of control is hereby authorized and empowered to issue certificates of appropriation under such permits as may be granted by the state engineer of Wyoming upon certification from the state engineer of Utah that the waters appropriated have been put to beneficial uses set forth in the permits. The state engineer and the board of control of Wyoming are also authorized and empowered to cooperate with the state engineer of Utah in the determination, supervision, regulation and control of all water and water rights on all interstate streams; and to these ends the state engineer and board of control of Wyoming, by and with the consent of the governor, may enter into the necessary agreements with the state engineer of Utah to carry out the purposes of this section; provided, that such agreements are not in conflict with the provisions of the irrigation laws now in force in this state; provided, further, that such authority shall not be exercised by the state engineer or board of control until after the state of Utah has passed a law granting its state engineer like authority to that granted to the state engineer and board of control of Wyoming by this section. The state engineer is further authorized and empowered to receive and grant applications to appropriate water from the Little Missouri River in Wyoming where such water is to be conveyed and used for beneficial purposes within the state of Montana, and the board of control is hereby authorized and empowered to issue certificates of appropriation under such permits as may be granted by the state engineer of the state of Wyoming, upon certification from the state of Montana that the waters appropriated have been put to beneficial uses set forth in the permit. Provided that the granting of any such permit for application to beneficial uses in the state of Montana shall in no manner impair or injure any existing water rights in the state of Wyoming.
W.S. 41-4-103