Registration plates must be used on the vehicle for which they were issued. They cannot be moved from vehicle to vehicle without the plate being transferred through an authorized PennDOT agent.
PA Vehicle Code Section 1372 states:
Unauthorized transfer or use of registration.
No person shall:
(1) allow a registration card or plate or permit to be used by any person not authorized to use it or on any vehicle other than the vehicle for which it was issued;
(2) use any registration card or plate or permit unless authorized to do so; or
(3) display a registration card or plate in, on or in connection with any vehicle other than the vehicle for which it was issued.