It shall be unlawful for any person not an occupant, owner or invitee to enter any private property enclosed by walls or fences with closed gates between the hours of six P.M. and six A.M. The provisions of this section shall not apply to any justifiable emergency entry or to premises which are not posted with clearly visible signs prohibiting trespass upon the enclosed premises. The provisions of this section are supplemental to existing law relating to trespass and punishment therefor. Any person who violates the provisions of this section shall be deemed guilty of a misdemeanor and upon conviction shall be fined not less than twenty-five dollars nor more than two hundred dollars or imprisoned for not more than thirty days.