Mont. Code Ann. § 2-1-209

2-1-209 . Concurrent jurisdiction over Fort Peck Dam ceded to United States -- reservation of rights to state. Consent to purchase or condemn all necessary lands is hereby given and concurrent jurisdiction is ceded to the United States over the Fort Peck Dam, the body of water or artificial lake created by the dam, the land under the body of water, and any lands now owned or that may be acquired by the United States and that touch the body of water, all such land and water being situated in the counties of Valley, Phillips, McCone, Garfield, Petroleum, and Fergus, state of Montana. The state reserves the right to serve civil or criminal process within the limits of the territory over which jurisdiction is ceded in any suits or prosecutions for or on account of rights obtained, obligations incurred, or crimes committed in this state, within or outside of the territory. The state also reserves the right to tax persons and corporations and their franchises and property within the territory. The state and its inhabitants, citizens, and nonresidents reserve the right to fish or hunt by boat or otherwise and the right of access, ingress, and egress to and through the ceded territory to all persons owning or controlling livestock for the purpose of watering the livestock. The state reserves jurisdiction in the enforcement of state laws relating to the duties of the department of livestock and the department of environmental quality and the enforcement of regulations promulgated by the departments in accordance with the laws of the state. Jurisdiction does not vest until the United States, through the proper officers, notifies the governor of the state of Montana that it assumes police or military jurisdiction over the territory.