Two Dead Romans Are Fighting Over the Moon

The legal dispute about who owns resources extracted from the Moon comes down, at its foundation, to two phrases from Roman property law that are roughly two thousand years old. This is either evidence of law's remarkable continuity or a sign that the legal profession has been quietly running out the clock on the same argument since the reign of Augustus. Possibly both.

The phrases are res nullius and res communis. Understanding what each one means, where each one came from, and why the distinction between them matters enormously in 2026 is genuinely useful. The billable hours currently being accumulated by space lawyers on this question alone could fund a modest lunar mission. Here's the short version.

Res Nullius: The Thing That Belongs to No One (Yet)

Res nullius translates directly as "thing belonging to no one." In Roman property law, it described objects that currently had no owner but were, in principle, capable of being owned. A wild rabbit before you caught it. A fish before you hauled it from the sea. Land that no one had claimed or cultivated. The key feature of res nullius is that it's ownable: the first person to take possession of it acquires a legitimate property right.

This concept traveled through Western legal history in a particularly consequential way. It underpins the doctrine of terra nullius ("land belonging to no one"), which provided the legal justification for European colonial settlement of territories that were, in fact, extensively occupied by people who did not organize their land relationships according to Roman categories. The doctrine held that land not cultivated or enclosed in a European manner was unowned, and therefore acquirable. The legal history of res nullius is also a history of deciding whose presence counts as ownership.

The application to space resources works as follows: before anyone extracts a tonne of water ice from a lunar crater, that ice belongs to no one. The party that extracts it acquires a property right through the act of extraction, just as a fishing vessel acquires rights to the fish it hauls aboard. The vessel doesn't own the ocean. It owns the fish.

Res Communis: The Thing That Belongs to Everyone

Res communis translates as "thing belonging to all." In Roman law, it described things that couldn't be privately owned because their nature made them common property: air, running water, the sea. No one could own the Mediterranean, which was inconvenient for those who might have liked to try. The defining feature of res communis isn't that it's unowned but that it's unownable: the thing can't be reduced to private property regardless of who gets there first.

The 1967 Outer Space Treaty established outer space and all celestial bodies as something close to res communis. Article II states 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." No nation can own the Moon. No nation can plant a flag and file a deed. This much is settled international law, signed by the US, Russia, China, and over a hundred other states.

What the OST doesn't settle is whether the resources on the Moon are also res communis, or whether they're res nullius that become ownable through extraction, even though the body they sit on can't be owned. That distinction, the gap between owning the Moon and owning a bucket of stuff you took from it, is where approximately all of current space law lives.

The 1979 Moon Agreement Tried to Settle This

The Moon Agreement, formally the Agreement Governing the Activities of States on the Moon and Other Celestial Bodies, was finalized in 1979 and came into force in 1984. It took direct aim at the ambiguity in the Outer Space Treaty. Its answer: lunar resources aren't res nullius. They're something more specific: "the common heritage of mankind."

Common heritage of mankind (CHM) is a legal concept developed in the context of deep-sea mining. It means that a resource belongs not just to all present nations but to humanity as a whole, including future generations, and that no exploitation of that resource should occur until an international regime has been established to govern it and to share the benefits equitably. Under the Moon Agreement, a commercial operator can't simply show up on the Moon, extract water ice, and sell it. Extraction requires a multilateral agreement about governance and benefit-sharing that doesn't yet exist and, given the current state of international relations, may not be imminent.

Eighteen nations ratified the Moon Agreement; as of early 2024, Saudi Arabia's withdrawal reduced the active party count to seventeen. None of them are major space powers. The United States, Russia, China, Japan, and the European space powers all declined to ratify. The treaty has legal force for its seventeen active members. For everyone else in the solar system, it does not.

The Fishing Analogy and Its Limits

The argument for treating lunar resources as res nullius relies heavily on the fishing analogy, and it's a reasonable one at first pass. Nations don't own the high seas. But fishing vessels can legally catch fish from the high seas and own what they haul in. The act of extraction, on this reading, creates property rights without requiring ownership of the commons itself. Several space-faring nations have enacted domestic law on this premise: the US in 2015, Luxembourg in 2017, the UAE in 2019, Japan in 2021. Each law grants its citizens the right to own, use, and sell resources extracted from space.

The analogy has limits. The high seas aren't the Moon. Fish are a renewable resource, notionally, under anything resembling reasonable management. Lunar water ice, once extracted from a permanently shadowed crater at the south pole, doesn't replenish. The south polar region of the Moon is a finite area. Specific crater locations are significantly more valuable than others due to their ice concentration and position relative to solar power and potential base sites. The res nullius framework creates first-mover advantages that may, over time, function as effective territorial control even if they don't technically constitute sovereignty.

This is not a hypothetical... it's the shape of the argument that will arise when two operators want to work the same crater.

The Deep Seabed Parallel

The closest real-world precedent is deep-sea mineral extraction. Vast polymetallic nodule deposits sit in international waters, and competing sovereign interests have wanted to mine them since the 1960s. Roughly fifteen years of negotiation produced Part XI of UNCLOS and the International Seabed Authority, designed to regulate deep-sea mining, collect royalties, and distribute proceeds to developing nations under the "common heritage" concept.

The United States helped design the framework, pushed for fewer benefit-sharing obligations, and declined to ratify it. It has operated within UNCLOS norms selectively ever since, through customary practice and the diplomatic reality that US companies need access to nations that did sign. The ISA has spent recent years under sustained pressure from mining industry interests to approve extraction before baseline environmental science is complete.

What the seabed example actually demonstrates: the framework produced reflected the interests of whoever dominated its drafting. The most powerful participant shaped the outcome while declining to formally join. The institution created to protect the commons ended up mediating between extraction industry interests and the science trying to catch up. Calling this "governance" is accurate in the technical sense. Holding it up as an aspirational model requires some selective memory about how it got built and who it has served.

The Moon is moving faster than that. The framework being assembled looks familiar.

What the Law Has Not Answered

No court has ruled on whether extracting and selling lunar resources constitutes prohibited "national appropriation by use" under Article II of the Outer Space Treaty. No court has jurisdiction to rule. The only international body that could have claimed that jurisdiction, the Moon Agreement's governing regime, doesn't exist because the treaty that would have created it has seventeen active parties and none of the relevant players among them.

The legal framework for lunar resource extraction is, at present, a set of contending domestic laws, a contested interpretation of a 1967 treaty, and a 1979 treaty that most of the parties with spacecraft have declined to join. Whether that constitutes res nullius or res communis will eventually be settled, as these things always are, by a combination of what actually happens and the diplomatic and legal effort deployed to characterize it afterward.

The Roman lawyers who coined these phrases were working on problems involving rabbits and river fish. They couldn't have anticipated that their vocabulary would determine the ownership of frozen water 384,000 kilometers from the nearest notary public. This is the kind of detail that makes history funny, if you catch it at the right moment.

We're at that moment now.

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