Mont. Code Ann. § 85-16-101

Any person or persons owning land bordering upon any of the navigable waters within the state are granted a license and permit to build docks and wharves over, across, and upon the lands under water belonging to the state. Such docks and wharves shall be extended out into such navigable water such distance only as may be necessary to permit all boats, steamboats, and vessels to safely land thereat and discharge and take on their cargoes and passengers.