N.J. Stat. § 45:8A-3
The officer or body having charge and control of any library within this State supported in whole or in part by public funds, except a board of education, may, in its discretion, require, and any officer or body having charge and control of any such library serving any municipality or group of municipalities having a population of 10,000 inhabitants or over, except a board of education, shall require that any person hereafter employed in such library in any professional office or position, that requires for adequate performance the knowledge and techniques of library science as taught in accredited library schools, shall hold a professional librarian's certificate issued by the State Board of Examiners as provided in this act. No such officer or body shall terminate the employment of or refuse to continue the employment or re-employment of any person holding a professional office or position at the time this act becomes effective for the reason that such person is not the holder of any such certificate.
N.J.S. § 45:8A-3