Any person who maintains any sign not authorized by this part and which was not lawfully in existence on October 6, 1971, shall be guilty of a misdemeanor. Each day or fraction thereof during which a sign is unlawfully maintained shall constitute a separate offense. The commissioner and officials or employees of the department designated by the commissioner are authorized to take such actions as may be necessary or appropriate to procure the prosecution and conviction of any person, firm, or corporation violating this Code section.