In addition to the exemptions now allowed by law, any person who shall have performed duty in the Pennsylvania National Guard for a period of nine years or who served for nine months or a longer period in active service of the United States and was honorably discharged or mustered out, shall be exempt from further military service, except in case of war, invasion or insurrection. Every officer and enlisted person of the Pennsylvania National Guard shall be exempt from jury duty during the period of his active service.