I WAS TOLD THAT YOU CAN HAVE AS DARK AS YOU WANT ON THE BACK, BUT YOUR FRONT WINDOWS CANT BE DARKER THAN 20 OR 30%... I HAD A LIMO TINT ON THE BACK ON MY LAST CAR
I got pulled over once by a state trooper for tint. I don't think regular cops care about tint. The fine in Missouri for illegal tint was only like $98.