53 Pa. Stat. § 3704
It shall be lawful for any number of persons owning or occupying real estate in any city, borough or township of this commonwealth, upon application to and with the approval of the court of quarter sessions of the proper county, to employ a night watchman or night watchmen for the purpose of protecting their premises and property in the night-time and all persons so appointed, with the approval aforesaid, as night watchman shall have, exercise and enjoy all the rights, powers and privileges, now vested by law in constables or police officers duly elected or appointed in said cities or boroughs: Provided, however, That such night watchmen shall not exercise the power of serving subpoenas or any civil or other process: Provided, That in any city having a department of public safety, all such applications shall be made to and granted by the director of said department under such rules and regulations as may be adopted by said department.
53 P.S. § 3704