I know a Federal LEO who was driving an unmarked car while searching for a guy. A local small town cop decided he wanted to ask him what he was doing so he pulled him over.
He asked for his identification and the officer showed it to him. The cop knew his stop was illegal but the officer just let it go. It did scare the guy tho.
Years ago a friend of mine was working undercover with the organized crime task force. He was visiting us and parked his car with out of state tags in front of our neighbor’s house. Ends up the neighbor was a jealous LEO’s girlfriend and the LEO ran my friends tags to find out whose car it was.
Even though it was a private car, my friends tags were flagged so that anyone running his tags were told that the system was not working at that moment and the DMV needed to take the requester’s information to call them back. The DMV immediately called my friend who confronted the LEO and wanted to know why he was running his tags! End of story real quick!