This is an excellent article describing the many issues surrounding the illegal and illegitimate use of temporary tags (vehicle registrations).
This also makes a person wonder why Cities like Philadelphia and San Francisco want to limit police investigations of vehicle registration including temporary tags.
Streetsblog found licensed used car dealers exploiting loose regulations to
sell real temp tags illegally.
— Read on www.streetsblogprojects.org/ghost-tags-part-1-the-dealers