FYI anyone in Fla. and maybe some other states. Several years ago while driving my custom built '84 El Camino (Turbo Buick V-6) @9 a.m. I turned into store parking lot downtown, started to get out and heard loud p.a. announce, " Sir, DO NOT GET OUT OF YOUR CAR!!". I looked up to discover a fully lit up police car in this little parking lot ready to apprehend a felonious criminal of the 1st degree. I stepped back, closed the door, immediately, placed my hands on the steering wheel waiting. When the officer arrived his first question was, " Do you know why I stopped you?" Of course I answered, " I was already stopped, and did not even know you were there, so I did not know you had even stopped me". This did not help. He then explained that Fla. statute #316.24 or such (have forgotten now, so better google exact #, it is really there), specifically forbids any part of a license plate from being covered so that it cannot be read from within 100', and there is something covering the letters, "ori" in the word "Florida" across the top of my license plate. Honestly. And, HE HAS A COPY IN HAND!
Of course I had to ask if he had nothing better to do at 9 a.m. on Saturday morning. "Do not take and Attitude with Me." I am not helping myself. Short version(it is much longer), after checking license, registration, insurance, he compliments my car(go figure), says he will give me a warning ticket even though I have an attitude problem(?). I later follow him down the street as he passes 2 Cadillacs and a new Lexus with full license surrounds that he does not stop. This cop has since been fired for excessive use of force on the job(Another story). I had planned to talk to the local Chief about him, wish I had, might have saved a women's life(another story).
When I picked up my F-Type, dealer license cover had full surround that covers bottom of the tag. Police forum talks about this statute that allows them to legally stop cars and search for anything they want. Be forewarned if you are in Fla.

 

This one happened a while back in a rental car, in the Netherlands! So probably doesn't count as a US police experience. But worthy story in my book...

8am in the morning, pulling out of Schiphol airport in Amsterdam in a newly rented vehicle, stopped by a very attractive police women and BREATHALYZED ! Result was negative, and it's the only time it has happened to me. Apparently they catch a lot of rental car drivers that have imbibed a little much on the trans-Atlantic flight. Later in that business trip, I got not 1, but 2 speeding tickets (~$150) from their 'average speed' cameras - smart B*&%^#%Ds those Dutch...