They are not illegal everywhere, and I've had one on my other car for 2 years, just got to make sure to turn it off to avoid getting hassled.
Laser Interceptor USA - Laser Jammer - Exclusive Factory Authorized Distributor to The USA and Canada - Laws: State By State
Theres a map of all the states, mine is there and its legal.
So back to my original question, how do you access the holes behind the license plate from the cabin of the car?