As for TN law, I am unsure. I grew up in VA and was stationed in MD. In both of those states, it is officer discretion. If the officer beleives that the lights are not visible from 1000 feet away (as per DOT regulations; all factory and aftermarket taillights adhere to this) a ticket can be issued and then debated in court. The light must be visible and be red in color for rear running lights and red or amber for turn signals. As long as you apply the coating in a responsible manner (i got the black look with just a hint of the red) it should be fine. I tested mine with the lighs on, and the running lights are visible from my apartment to the car no problem. But I am neither a lawyer or a state trooper, just got pulled in Baltimore multiple times for having blackout covers on my MX3 headlights after dark. I may be wrong. As for where to look, call the state police in TN and ask.