I don't know if it's still in effect, but the law that makes cops exempt from traffic laws, states that they can only break the traffic laws while their emergency equipment is on ( lights and/or siren). Which means that if he was pacing you with his lights and siren off then he was speeding and not exempt from traffic laws. so how is he going to tell you not to speed while he is doing it??? like I said, I don't know if this is still in effect but it was several years ago and I can't see a reason to change it. just something to look up.