Who Governs Mars? Mars Colony Law, the Outer Space Treaty and the ‘Free Planet’ Clause

Mars colony law sounds like a question for the far future, but the main rules already exist. They were written in the 1960s, long before private companies talked about cities on another planet. SpaceX says it was founded with “the ultimate goal of enabling people to live on other planets”, and NASA has spent years planning for crewed Mars missions. Whenever the first people land, they will arrive under a legal framework that is already in force for 116 States.

Mars is covered by the Outer Space Treaty

The Outer Space Treaty applies to “outer space, including the moon and other celestial bodies”. Mars is a celestial body, so every article of the treaty that mentions them applies to it. According to UNOOSA’s status table as at 1 January 2025, the treaty has 116 States Parties, including the United States, Russia, China, India and Japan. For a full walk-through see our Outer Space Treaty explainer.

Four provisions matter most for a settlement.

Article II says outer space, including celestial bodies, “is not subject to national appropriation by claim of sovereignty, by means of use or occupation, or by any other means”. No State can claim Mars or any part of it, however long its people have lived there.

Article IV says celestial bodies shall be used “exclusively for peaceful purposes” and forbids “the establishment of military bases, installations and fortifications” on them. Military personnel may take part in scientific or other peaceful work, but a Mars settlement could not be a military outpost.

Article IX requires States to explore celestial bodies “so as to avoid their harmful contamination” and to avoid adverse changes to Earth’s environment from extraterrestrial matter. It also requires consultations before an activity that could cause harmful interference with other States.

Article XII says all “stations, installations, equipment and space vehicles on the moon and other celestial bodies shall be open to representatives of other States Parties” on a basis of reciprocity, with reasonable advance notice.

Whose law applies on a Mars base?

There is no Martian legal system. Two treaty provisions work together instead.

Article VI makes States internationally responsible for “national activities in outer space”, whether carried out by government agencies or by “non-governmental entities”, and requires that private activities have “authorization and continuing supervision by the appropriate State Party”. A private Mars settlement would therefore need a State on Earth to license it and keep supervising it for as long as it exists.

Article VIII says the State on whose registry a space object is carried “shall retain jurisdiction and control over such object, and over any personnel thereof, while in outer space or on a celestial body”. It adds that ownership of objects, “including objects landed or constructed on a celestial body”, is not affected by their presence there.

Put together, a habitat built by a US company and registered by the United States would be under US jurisdiction, and US law would apply inside it. A neighbouring module registered by another State would carry that State’s law. That is how the International Space Station already works: each partner keeps jurisdiction over the modules it registers and over its own nationals. The Registration Convention is what makes this work in practice, because it records which State is responsible for which object.

Distance makes this harder. A NASA study of crewed Mars missions puts the maximum one-way communication delay at about 22 minutes. A court, regulator or police force on Earth cannot act in real time. In practice, day-to-day governance would sit with the mission commander and the operator’s internal rules, backed by the national law of the registering State. In US practice, for example, NASA’s rules give the commander of a NASA mission “absolute authority” over order and safety on board, including the power to restrain a person until they can be handed to the proper authorities.

The “free planet” clause

In 2020, the beta terms of service for Starlink, SpaceX’s satellite internet service, included a section on services provided on Mars or in transit to Mars. It said the parties “recognize Mars as a free planet” and that no Earth-based government has authority or sovereignty over Martian activities, with disputes to be settled by “self-governing principles”. Antonino Salmeri, writing in SpaceNews in November 2020, argued that the clause was void under the Outer Space Treaty.

The objection is simple. Article VI makes the United States responsible for authorising and supervising SpaceX’s activities in space. A contract between a company and its customers cannot release the United States from that duty or bind other States. Article II also stops any State claiming Mars as territory. The clause is best read as a statement of aspiration rather than law, and I am not aware of any government that has endorsed it.

Who can own what on Mars?

Article II stops anyone claiming the land. Article VIII confirms that ownership of hardware landed or built on a celestial body is unaffected.

Resources are the contested part. The US Commercial Space Launch Competitiveness Act of 2015 says, in 51 U.S.C. section 51303, that a US citizen engaged in commercial recovery of a “space resource” is entitled to possess, own, transport, use and sell it, “in accordance with applicable law, including the international obligations of the United States”. The law applies to Mars as much as to the Moon or asteroids. The Artemis Accords apply to activities on “the Moon, Mars, comets, and asteroids” and in orbit of the Moon or Mars, and Section 10 affirms that extracting space resources “does not inherently constitute national appropriation”. NASA says San Marino became the 76th signatory on 25 September 2026. I set out the arguments on both sides in our piece on who owns the Moon, and they apply equally to Mars.

The 1979 Moon Agreement takes a different line. Article 1 extends its rules on the Moon “to other celestial bodies within the solar system, other than the earth”, and Article 11 declares the Moon and its natural resources “the common heritage of mankind” and bars ownership of resources “in place”. But UNOOSA records only 17 parties as at 1 January 2025, and the United States, Russia, China, Japan and the United Kingdom are not among them. Our Moon Agreement explainer covers why.

Planetary protection: the rule that bites first

The first binding constraint on any Mars settlement will probably be contamination, not property. Article IX’s ban on “harmful contamination” is a treaty obligation, and Mars is where it matters most, because scientists still want to know whether Mars has or had life.

The detailed rules come from the Committee on Space Research. The COSPAR Policy on Planetary Protection is a non-legally binding international standard, but space agencies apply it through their own requirements. It puts Mars landers in Category IV, its strictest for outbound missions, and treats any return of material from Mars as Category V “restricted Earth return”. Its principles for human missions say planetary protection goals “should not be relaxed to accommodate a human mission to Mars” and that safeguarding Earth from back contamination “is the highest planetary protection priority in Mars exploration”.

In the United States, NASA issued an interim directive on planetary protection for human missions to Mars in July 2020, covering NASA missions, joint missions and commercial missions NASA sponsors. It states that the treaty “sets forth legal requirements on U.S. governmental and nongovernmental entities”. A purely private mission would fall outside NASA’s directive. The nearest existing federal check is the FAA’s payload review under 14 CFR 450.43, which asks whether a payload’s launch would jeopardise, among other things, “international obligations of the United States”.

Citizenship, families and self-government

A child born on Mars would not be born in any State’s territory, because Article II forbids that territory from existing. Nationality would depend on the parents’ own citizenship laws. US law, for example, in 8 U.S.C. section 1401, grants citizenship to a person born outside the United States to two US citizen parents, one of whom has lived in the United States, with further rules where only one parent is a citizen. Other States’ laws would produce different answers.

Under Article III of the Liability Convention, damage caused “elsewhere than on the surface of the earth” by one State’s space object to another’s is compensated only on proof of fault. On Mars, one base damaging another would be a fault-based claim between the States responsible.

The nearest model for shared governance on Earth is Antarctica. Under Article IV of the Antarctic Treaty, nothing done while the treaty is in force can support or create a claim to territorial sovereignty, and the treaty now has 58 parties. States run research stations there without any of them gaining sovereignty, with a common treaty system on top. A Mars settlement under the Outer Space Treaty would look similar, but without an equivalent of the Antarctic Treaty’s detailed system of meetings, inspections and environmental rules.

What I would watch

The first is licensing. Article VI means the first private Mars mission will need a licensing State. How a State authorises and supervises a mission it cannot reach for months will shape Mars colony law more than any treaty debate.

The second is planetary protection for crewed missions. If COSPAR’s work on human missions is written into national licensing conditions, it will become the most detailed binding law for any settlement.

The third is the Artemis Accords. With 76 signatories, the Accords already reach Mars in their scope. Any future implementing work on deconfliction and safety zones will probably be drafted for the Moon first and then carried to Mars.

The fourth is a governance agreement. At some point a settlement with people from several States will need something like the ISS Intergovernmental Agreement, covering jurisdiction, criminal law and dispute settlement. I am not aware of any negotiation on that.

Anuj KumarEditor-in-Chief

Anuj Kumar is the founder of Legal Desire Media and publishes Fashion Law Journal and Space Law Journal.

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