65 Pa. Stat. § 1
Every person who shall hold any office, or appointment of profit or trust, under the government of the United States, whether an officer, a subordinate officer or agent, who is or shall be employed under the legislative, executive or judiciary departments of the United States, and also every member of congress, is hereby declared to be incapable of holding or exercising, at the same time, the office or appointment of justice of the peace, notary public, mayor, recorder, burgess or alderman of any city, corporate town or borough, resident physician of the lazaretto, constable, judge, inspector or clerk of election under this commonwealth: Provided, however, That the provisions hereof shall not apply to any person who shall enlist, enroll or be called or drafted into the active military of naval service of the United States or any branch or unit thereof during any war or emergency as hereinafter defined.
65 P.S. § 1