Indeed, airwaves in the US are public, and the FCC allocates spectrum to transmitters. But there's no law blocking who is allowed to listen on a given frequenc

Indeed, airwaves in the US are public, and the FCC allocates spectrum to transmitters. But there's no law blocking who is allowed to listen on a given frequency. Read up on the Radio Act of 1927 for rationale. See also Executive Order 13642, "Making Open and Machine Readable the New Default for Government Information".