From: Brent on

Last night on the edens expressway I come across a white crown vic
police interceptor... complete with extra antenna, cow catcher push bar
on the front, cage in the back, basically all the cop equipment minus
the rollers. The car was wearing those LE plates.
http://www.cyberdriveillinois.com/departments/vehicles/license_plate_guide/specialty_plates/police_memorial.html

Someone did themselves an Elwood Blues car purchase and then very
carefully built it back up with all the stuff that the cops strip off
that's legal to put back on. Then they add a 'law enforcement' plate
issued by the state government. It was a rather convincing package
without examining it for a bit of time. I still let the mercedes with
one working head lamp pass that CV first.

Looks like IL offers at least two 'cop' plates:
http://www.cyberdriveillinois.com/departments/vehicles/license_plate_guide/specialty_plates/ilpolice.html

So, what happens when one of these wannabes pulls someone over and
commits a crime?