Unless you’ve been living under a rock you have seen selective law enforcement. Favoritism, political force, racism. There are good cops, bad cops, and I think the majority just trying to do their job and make it home at the end of the day.
 
There is a cadre of laws that are rarely enforced but remain a tool for the cop to use if he/she is pissed.
One of those laws is blocking/obscuring any part of the license plate.
More recently they have taken more interest because of the red-light cameras and automatic toll collecting.
Over the years I’ve seen hundreds, maybe thousands of frames, many installed by dealers for advertising, that at least partially block a lot of the information like the name of the state.
 
I recently saw this plate on some late model Jeep SUV. The engraved metal chrome plated frame covered everything but the strip across the middle where the number would be. I’d guess it’s a PA plate since it was in PA, white with blue letters in the PA font. I know for sure it’s illegal as hell but probably won’t be questioned unless he pisses off a cop.