Since the federal government did (in effect) legislate the matter (federal legislation is the legal equivalent of federal law), 91-36 renders all state and local law on the subject (only on the subject it addresses) totally void. Local courts can't overrule the federal government. Just print up a copy and keep it in your car. If an officer still insists on writing a ticket, it's capricious enforcement (or whatever your local law calls it) and you're most likely entitled to payment for your time and trouble needed to inform the court to throw the charge out. (And unless the officer has some expertise that's relevant in a court, "scanner" and "transceiver" don't enter into the matter, since he won't be able to effectively testify which it was that you were running.)