Me. Stat. tit. 23 § 1151
No person shall place, maintain or display upon or in view of any highway any unauthorized sign, signal, marking or device which purports to be or is an imitation of or resembles an official traffic-control device or railroad sign or signal, or which attempts to direct the movement of traffic, or which hides from view or so interferes with the effectiveness of any official traffic-control device or any railroad sign or signal as to endanger the public, and no person shall place or maintain nor shall any public authority permit upon any highway any traffic sign or signal bearing thereon any commercial advertising. This shall not be deemed to prohibit the erection upon private property adjacent to highways of signs giving useful directional information or promoting highway safety and of a type that cannot be mistaken for official signs. Any person, firm, corporation or political subdivision of the State, while working on, under, over or immediately adjacent to any highway may erect temporary warning or directional signs or signals for the purpose of safeguarding or protecting its workmen and facilitating and protecting travel along the highway by the traveling public.
Every such prohibited sign, signal or marking is declared to be a public nuisance and the authority having jurisdiction over the highway may order the same removed and, if not removed within 48 hours after receipt of the notice, is empowered to remove the same or cause it to be removed.
23 M.R.S. § 1151