Mont. Code Ann. § 87-2-305

Navigable rivers, sloughs, or streams between the lines of ordinary high water thereof of the state of Montana and all rivers, sloughs, and streams flowing through any public lands of the state shall hereafter be public waters for the purpose of angling, and any rights of title to such streams or the land between the high water flow lines or within the meander lines of navigable streams shall be subject to the right of any person owning an angler's license of this state who desires to angle therein or along their banks to go upon the same for such purpose.