Where in the Federal Communications Commission's governing legislation does it say that they're only allowed to regulate things sent through the airwaves?
It applies to communications over radio or wire: “The provisions of this act shall apply to all interstate and foreign communication by wire
or radio and all interstate and foreign transmission of energy by radio, which originates and/or is received within the United States, and to all persons engaged within the United States in such
communication or such transmission of energy by radio, and to the licensing and regulating of all radio stations as hereinafter provided…”
It applies to communications over radio or wire: “The provisions of this act shall apply to all interstate and foreign communication by wire or radio and all interstate and foreign transmission of energy by radio, which originates and/or is received within the United States, and to all persons engaged within the United States in such communication or such transmission of energy by radio, and to the licensing and regulating of all radio stations as hereinafter provided…”