Sounds like one of those class-action lawsuit commercials: "If you or someone you know has been diagnosed with any form of rep-related powerlessness, call now"
My guess is that at some point, there will need to be a transponder with ID on them to make it easier to identify when they are in the air. As it stands now, you either force the thing down or follow it to the landing area and then confiscate it and check who owns it
Without the registration, someone could crash it into a crowd/thing/white house lawn and simply walk away. There are fewer options to tell who it belongs to
(I don't recommend the last one...and if you do, don't be a drunk secret service agent that shows up to investigate later)