The Simple answer is that no, it is not illegal, thanks to the Communications Act of 1934. This states that radio frequencies – including those used by the cops – are public property and so anyone can listen to them. Hooray! If you are listening to these channels out of curiosity then you’ll be fine. Any good lawyer would advise you however to take some precautions, and bear in mind there are some legal loopholes that can get you into trouble. For example, many states, such as New York, have made it illegal to use a scanner whilst driving a vehicle.