N.J. Stat. § 40:47-4.7
Notwithstanding the provisions of law as to maximum age, residence, eligibility for membership in a pension or retirement system, duration of employment throughout an entire year or restriction on employment or earnings upon eligibility of any person to continued receipt of retirement benefits, any municipality may by ordinance authorize the temporary appointment to its police department or force, for a period not in excess of 4 years, of any citizen of the United States of good moral character who has had 10 or more years of experience in former employment as a member of the police force or other law enforcement agency of the United States or of this or another State, or of a county or municipality of this or another State.
N.J.S. § 40:47-4.7