A treaty written before the first landing
In 1967 no human had yet set foot on the Moon, and no nation had put a weapon in orbit. Yet diplomats were already drafting rules for those possibilities. The result was the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies, generally called the Outer Space Treaty. It was opened for signature on 27 January 1967 in Washington, London and Moscow, and it entered into force on 10 October 1967.
The date is notable for another reason. Late on the same day, the Apollo 1 crew died in their launch pad fire, so the treaty’s signing and a major space tragedy happened within hours of each other.
How it came about
The treaty followed several years of work at the United Nations, mainly in its committee on the peaceful uses of outer space. In the early Cold War, many people feared that space would be turned into another arena for weapons. The superpowers each had reasons for wanting some limits: neither wanted the other to place nuclear weapons overhead, and neither wanted to see claims of ownership stake out the Moon.
Earlier steps included the 1963 Partial Test Ban Treaty, which prohibited nuclear tests in space among other places, and a set of principles adopted by the United Nations General Assembly in 1963. The 1967 treaty turned many of these ideas into binding legal text for the states that joined. Drafts were negotiated chiefly between the United States and the Soviet Union, with many other countries contributing. Dozens of states signed on the opening day, and the United States Senate gave its consent to ratification in the spring of 1967.
The core principles
The treaty is short, and its main ideas can be listed plainly:
- Freedom of exploration. Space, the Moon and other celestial bodies are open to exploration and use by all states, and this is to be done for the benefit of all countries.
- No national appropriation. Outer space and celestial bodies cannot be claimed by any nation by declaring sovereignty, by use or occupation, or by any other means.
- No weapons of mass destruction in orbit. States agree not to place nuclear weapons or other weapons of mass destruction in orbit around the Earth, on celestial bodies, or in outer space in any other way.
- Peaceful use of the Moon. The Moon and other celestial bodies are to be used exclusively for peaceful purposes. Military bases, fortifications and weapons tests on them are banned.
- Astronauts as envoys. Astronauts are to be regarded as envoys of mankind, and states are to help them in case of accident or emergency landing.
- Responsibility and liability. States bear international responsibility for national activities in space, including those carried out by private companies, which need authorisation and supervision. A state that launches an object is liable for damage it causes.
- Registration and caution. Launching states keep a registry of objects, and they are to avoid harmful contamination of space and of the Earth’s environment from space activities.
What it does not say
The treaty is sometimes described as banning all weapons in space, which is not accurate. The ban on orbital weapons applies to nuclear weapons and other weapons of mass destruction. Conventional weapons, and military uses of space such as reconnaissance and communications satellites, are not prohibited in the same way. The restrictions on military activity on the Moon are stricter than those for orbit.
It also leaves some questions open. The ban on national appropriation does not clearly state whether companies or individuals can own resources taken from asteroids or the Moon. Countries and scholars have interpreted this point differently, and it remains debated. A later agreement from 1979, the Moon Agreement, tried to add detail, but only a small number of states joined it, and the major space powers did not.
Why it was acceptable in 1967
The treaty arrived at a moment when the space race was intense, but it cost both sides little. It did not stop either from continuing a lunar programme. It reassured countries without space programmes that they would not be shut out of a global commons, and it eased concern about weapons overhead.
At the time, the treaty was also part of a broader effort at arms control in the 1960s, in a decade that included crises, as well as agreements. The Six-Day War of June 1967 and the escalating Vietnam War showed how fragile international calm was, and the space treaty stands as one area where agreement was reached.
Its legacy
More than a hundred states are now parties, including all major spacefaring nations. The treaty remains the foundation of space law. It informs later agreements on rescue of astronauts, liability for damage and registration of space objects. In recent decades, as private companies launch spacecraft and governments plan returns to the Moon, its principles have again become a subject of discussion.
The treaty is a short document with an outsized role. It was written when space seemed a place where two rivals could set rules before problems arose, and it has proved durable in a way many Cold War agreements did not.