Outer Space Treaty

The treaty developed through United Nations discussions on legal principles for space activities during the Cold War. The UN General Assembly commended the treaty text in Resolution 2222 (XXI) on 19 December 1966. It was opened for signature in London, Moscow and Washington on 27 January 1967, and entered into force on 10 October 1967. Its three original depositary governments were the United States, the United Kingdom and the Soviet Union. The UN Treaty Collection provides the treaty's registration and participant records.

The treaty says exploration and use of outer space, including the Moon and other celestial bodies, should be carried out for the benefit and in the interests of all countries. It makes outer space free for exploration and use by all states, with free access to celestial bodies, and protects freedom of scientific investigation and international cooperation. It also bars national appropriation of outer space and celestial bodies through sovereignty claims, use, occupation or other means. These principles establish that no state may claim celestial territory as sovereign national territory under the treaty.

The treaty prohibits states parties from placing nuclear weapons or other weapons of mass destruction in orbit, installing them on celestial bodies, or stationing them in outer space in another manner. It provides that the Moon and other celestial bodies are to be used exclusively for peaceful purposes, and prohibits military bases, weapons testing and military manoeuvres there. The text does not prohibit military personnel from conducting scientific research or other peaceful activities, nor the use of equipment needed for peaceful exploration.

States parties bear international responsibility for their national activities in outer space, whether undertaken by government agencies or non-governmental entities. Non-governmental space activities require authorization and continuing supervision by the appropriate state. The treaty also establishes international liability for damage caused by a state's space object in specified circumstances, addresses jurisdiction and control over registered space objects and personnel, and calls for assistance to astronauts in distress. These provisions make national governments central actors in the oversight of public and private space activity.

The treaty remains a foundation of international space law and is complemented by later agreements addressing matters such as astronaut rescue, liability and registration. It supplies broad principles rather than detailed answers to every modern issue, including commercial resource use and orbital congestion. The UN Office for Outer Space Affairs provides the treaty text and records of its negotiation; the UN Treaty Collection lists participant actions, which can be consulted for up-to-date treaty status.