Pennsylvania Statutes Title 3 P.S. Agriculture § 459-504-A. Control of dangerous dogs

It is unlawful for an owner or keeper of a dangerous dog to permit the dog to be outside the proper enclosure unless the dog is muzzled and restrained by a substantial chain or leash and under physical restraint of a responsible person. The muzzle shall be made in a manner that will not cause injury to the dog or interfere with its vision or respiration but shall prevent it from biting any person or animal or from destroying property with its teeth.