There are three bolt? -like fasteners.
Looking at the photo, notice the three large indentations.
Each large indentation has an unusual rivet ? like fastener
Look at the close-ups to see the fasteners.
As far as I can determine, there's no access to behind.
Photos including closeup below, TY.
(Note - the four small holes in the plastic are nothing, that's just where you attach the license plate to this holder. The problem is the three large openings where this holder is attached to my bumper.