The Sky’s Not the Limit: Legal Bonds and Boundaries in Claiming Sovereignty over Celestial Bodies

That the claiming of sovereignty on celestial bodies is a topical issue, one that might get newspapers’ headlines in the near future, is pretty evident. Public entities as well as private actors are studying, if not explicitly scheduling, missions destined to land on the Red Planet and colonize it. What about the law regulating such conduct? In the last decade or so, we have witnessed a revival of legal studies on space affairs, and those relating to the legality of the extraction of planetary resources have in particular flourished. However, the possibility of asserting sovereignty over those bodies, or part thereof, did not partake in such revival. This contribution takes the issue seriously, as it aims to understand which rules apply when we reach the final frontier. The same old answer: ‘the Outer Space Treaty applies’ is not satisfactory, for a number of reasons that relate to its uncertain legal status and even its somewhat uncertain content. These factors might prevent the scramble for Mars from being legally hindered. Irrespective of the treaty’s status, someone might try to establish a colony on a celestial body. This contribution analyzes the conditions under which the space homesteaders would be entitled to lay a valid sovereign claim on it; conversely, it answers the question whether the Earthlings would be bound to a duty of non-recognition of the new entity. A problem remains open: is there a possibility that international law at the (final) frontier might turn into the frontier of international law?