✔ 最佳答案
Well in maritime/admiralty law, they will often go by the nationality of the vessel, so if any dispute over jurisdiction, if something happens in international waters, or when the ship is otherwise not sailing in areas that some other nation can exercise jurisdiction, they go by its registered flag state. If no registered flag or nationality of the vessel is able to be established, then it would go by its last port of call.
So in your moon example, probably whichever country his space ship took him to the moon on or where the spaceship was registered at. If no spaceship flag registration, and built by a bunch of space pirates or something, then would likely go by space ship's last port of call, so unless the space ship first stopped off on another planet that had its own justice system, wanting to exercise jurisdiction over the case, it would have had to come from a place on earth, and it would be the country on earth where the space ship launched from.
So probably US, Russia or China, as we're the only three countries on earth who have done space launches.
However, like the other poster said, if modeled after the Antarctica Treaty, then could be different if there was such a treaty in effect at the time. Otherwise it would likely default to the old maritime/admiralty laws, which some laws go back over a thousand years. Literally. Because for over a thousand years, we've been sailing the earth and bad stuff happens sometimes out in the middle of the ocean, and we've had to come up with ways to deal with them.