53 Pa. Stat. § 17096
Any patrol or watchman, selected and employed by and at the private expense of the residents or of persons doing business in any block or blocks, square or squares, or parts thereof, in the city of Philadelphia, for the purpose of protection to their property therein against loss by fire, theft or robbery, shall, upon filing with the mayor of said city a certificate of such employment, the time for which he may have been so employed, and the bounds of the locality which they are required to watch, signed by the persons so employing him, whereupon, if the mayor is satisfied that such person is qualified, by his integrity and vigilance, to perform such duty, he shall have authority to appoint and commission him as patrol or watchman for such locality, with all the powers of policeman, in respect to the arrest of all vagrants and persons found offending against the law within the bounds of said locality, and all vagrants and offenders arrested by such patrol or watchman shall be received and held in custody at any police station, in like manner as if the arrest had been made by any policeman of said city; such patrol or watchman, when on duty, shall have authority to carry and use, when necessary, the usual implements of policemen for alarm, arrest and defence, and shall respond to the signals of policemen within the limits of their said locality, in making arrests and performing needful duty, but shall not be required to leave their said locality; and policemen shall in like manner respond to the signals of such patrol or watchman, and give him all needful aid in making arrests and protecting property within the limits of said locality; nothing in this act contained shall authorize any expenditure or liability whatever against the city of Philadelphia.
53 P.S. § 17096