Montana Title 61. Motor Vehicles § 61-8-210. Display of unauthorized signs, signals, or markings

(1) A person may not place, maintain, or display upon or in view of a highway any unauthorized sign, signal, marking, or device that purports to be or is an imitation of or resembles an official traffic control device, that attempts to direct the movement of traffic, or that hides from view or interferes with the effectiveness of any official traffic control device or flag person.

(2) A person may not place or maintain and a public authority may not permit commercial advertising on an official traffic control device on a highway, except for business signs included as a part of official motorist service panels or roadside area information panels approved by the department of transportation.

(3) This section does not prohibit the erection of signs upon private property adjacent to highways that give useful directional information and that are of a type that cannot be mistaken for official signs.