Nobody may own the Moon

Why did spacefaring states renounce claiming celestial territory before anyone could reach it?

The Outer Space Treaty entered into force in October 1967. Its second article says that outer space, including the Moon and other celestial bodies, is not subject to national appropriation by claim of sovereignty, by means of use or occupation, or by any other means. Two years before Apollo 11, the states most likely to get there first signed away the right to plant a flag that meant anything.

That is odd behaviour for great powers in the middle of a rivalry. Nobody renounced Antarctica outright, and the ordinary pattern of history is that reachable territory gets claimed. So why here, and — more interestingly — why then, before anyone had arrived?

Take the timing first, because it is the load-bearing part. Ask what a claim to the Moon would have been worth to the United States in 1967, when it was clearly ahead. It looks like an asset. But run the consequence forward. Territorial title in international law is not a thing you hold; it is a thing others recognise. An unrecognised claim buys you nothing except an obligation to defend it. And the only way to make a claim recognisable in the traditional way is effective occupation — permanent presence, which on the Moon means permanent, garrisoned, resupplied presence, for as long as you want the claim to survive.

So the option to claim is not free. Holding it open means that if the other side ever plants a flag, you must either match the expenditure or concede the precedent. Which means the real choice in 1967 was never "we own the Moon or we do not". It was "we both spend indefinitely contesting a place with nothing on it, or neither of us does".

Now the second question: why sign early? Consider what each side knew. Neither could be confident of its position twenty years out — the Soviet Union had led in 1957 and trailed by 1967, and the reversal had taken a decade. Under that uncertainty about who would end up standing where, both sides were negotiating over an outcome neither could yet claim. Bargaining is easiest precisely when no one knows which side of the bargain they will be on. Wait until there is a base with people in it, and the interests have hardened, the asset exists, and no agreement is reachable.

That is a commitment device in the strict sense: a party deliberately destroys one of its own options because possessing that option is what would drag it into a costly outcome. The point is not that claiming the Moon is wrong. The point is that being able to claim it is what makes the race unavoidable.

Which raises the question every commitment faces — why would anyone believe it? A promise not to do something you would later want to do is normally worth little. So what makes this one hold? Two things, and the first is unusual. A territorial claim only has value if others honour it, so a state that defected would gain nothing at all: it would end up with an announcement. Compare a treaty banning a weapon, where the defector ends up holding the weapon whatever anyone says. Non-appropriation is close to self-enforcing because the thing being renounced is a social fact rather than a physical one. The second is breadth — well over a hundred states are party, including every spacefaring one, so there is no coalition available to a defector that would make a claim stick.

Note the earlier attempt, too. The Antarctic Treaty of 1959 did not abolish territorial claims; it froze them, agreeing that nothing done while it was in force would strengthen or weaken any existing claim. That is what remains available once claims exist. Space had none yet, so the stronger move — renunciation rather than suspension — was still on the table. Commitment gets cheaper the earlier you make it.

Where does the argument strain? Exactly where the treaty stops. It bars appropriation by states; it says less about what may be extracted and sold. Since 2015 the United States, Luxembourg, the United Arab Emirates and Japan have each legislated that their nationals may own resources they recover, on the reading that mining ice is like fishing in the high seas rather than like annexing the sea. The Artemis Accords of 2020 add "safety zones" around operations, which their signatories insist are not territory. Whether all this respects the commitment or quietly hollows it is genuinely unsettled, and the states that have not signed the Accords say the latter. The 1979 Moon Agreement, which tried to close the gap by declaring lunar resources the common heritage of mankind, attracted fewer than twenty parties and not one major spacefaring power.

Three corrections worth making.

First, non-appropriation is not the same as a ban on ownership. Objects launched into space remain the property of the launching state, and a landed rover does not become common property. What cannot be owned is the place.

Second, the treaty was neither pure idealism nor pure cynicism — it was both, and reading it as only one misses why it held. The drafters plainly meant the language about the province of all mankind, and were also avoiding a race neither could afford on top of the one already running.

Third, a commitment is only as strong as the boundary of what it forbids. This one drew that boundary around sovereignty, which was the recognisable threat in 1967, and left resource use undefined because in 1967 it was not a live question. The strain the regime is under now sits exactly along that line.

• How the deep seabed regime tried the common-heritage route and what happened to it.
• Whether a permanently inhabited lunar base creates de facto territory that the treaty's words cannot reach.
• What "safety zone" would have to mean to stay distinguishable from a border.

Every term the collection defines is gathered in the glossary.