Gizmodo posted an article last week questioning if Elon Musk’s Crazy Mars Plan is Even Legal, but the summary is basically this:
In the United States, the Federal Aviation Administration (FAA) has jurisdiction to license what goes up into orbit, and what comes back down to Earth. But as soon as you’re in orbit, or heading to another celestial body, the rules start to get fuzzy. “At the moment, there is no legal regime for on-orbit activities,” Gabrynowicz said.