As far as I know, in every state there are laws preventing you from either covering your license plate with something, or from using any sort of active defense

As far as I know, in every state there are laws preventing you from either covering your license plate with something, or from using any sort of active defense mechanism. I have seen people experiment with reflective letters all around their license plate that are then detected by ANPR, resulting in it unable to determine what the real plate numbers are. This would seem to be legal. I suspect you could even make them reflective to IR while being invisible to the naked eye so your car wouldn't look like crap.