Under the terms of the Outer Space Treaty, outer space - including Mars - is under no jurisdiction, but objects and people launched into space are under the jur

Under the terms of the Outer Space Treaty, outer space - including Mars - is under no jurisdiction, but objects and people launched into space are under the jurisdiction of the country they launched from. The OST prohibits a signatory to the treaty from claiming any celestial body. In practical terms, a base on Mars would, unless it was exclusively built with components launched from the same country, be a patchwork of jurisdictions. This is in fact the situation with the ISS, which is (probably) the only place in the Universe where the territories of USA, Canada, Japan, Russia and Europe are only seconds apart. Of course there is always the possibility of a New Boston Tea Party. International convention is that a seceding state isn't bound by the treaties of the original state, so if a Martian government were recognized by Earth's governments they could try to claim Mars. The more practical concern is what it would mean for SpaceX to "claim Mars". I could claim Mars right now, but it wouldn't benefit me at all unless my claim was respected by other states. If the US, or anyone else, could steamroll in and take control of a SpaceX-founded colony that was purporting to be independent, then the claim would be worthless.