The 1967 Outer Space Treaty explicitly forbids any government from claiming ownership of any celestial object or the empty space in between them.
100 nations have signed and ratified this treaty, including all those currently with a space programme.
The treaty doesn’t specifically mention ownership claims by individuals or corporations though and this loophole has been exploited by entrepreneur Dennis Hope, among others, to justify selling plots of land on the Moon. The 1979 Moon Treaty attempted to close this loophole, but virtually no countries signed up to it.
Videogame developer Richard Garriott bought the Russian Lunokhod 2 rover for $68,500 at auction in 1993. Since this rover is still on the Moon, Garriott might be able to claim ownership of at least part of the lunar surface.
In practice, claiming ownership and enforcing that claim are very different things. Consider the geostationary orbit. This area of space is commercially valuable and relatively crowded. Individual satellites are allocated 70-kilometre (43-mile)-wide slots. Some of the equatorial countries tried to claim a slice of the geostationary orbit as part of their airspace back in 1976, but everyone ignored them.
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