N.J. Stat. § 58:5A-1
Any district water supply commission owning, operating, controlling and maintaining any watershed property, reservoir and water system within this State and the governing body of any municipality owning, operating, controlling and maintaining a watershed property exceeding three thousand acres in area and a reservoir and water system may, by resolution, appoint and establish a constabulary for the purpose of preserving order thereon and of protecting, regulating and controlling the same and its pumping stations, dams, pipelines, buildings, machinery and structures located thereon and of enforcing rules and regulations promulgated from time to time by said commission or by the governing body of said municipality for said purpose.
N.J.S. § 58:5A-1