Tony/Steve
Here's the thing, Tony. You can turn yourself on for creating Ultron. Other crazy scientists can be held accountable by their respective governments, or by another one if they commit a crime in another country. As for us, people know how to get ahold of me if they want to try to arrest me or an Avenger for a crime. So who are you trying to punish? Who are we registering? Asgardians?