72 Pa. Stat. § 6184
It shall be unlawful for any city, borough, or incorporated town or township to impose by ordinance or exact or collect under the provisions of any ordinance heretofore or hereafter enacted any license tax or fee upon or from any manufacturer or the agent, representative, or employe of any manufacturer who is a resident of the Commonwealth for soliciting orders for or for selling any goods, merchandise, or wares manufactured within this Commonwealth that is not or cannot legally be imposed upon or exacted or collected from any manufacturer or dealer or the agent, representative, or employe of any manufacturer who is a nonresident of the Commonwealth for soliciting orders for or for selling any goods, merchandise, or wares manufactured without the Commonwealth.
72 P.S. § 6184