Outer Space Treaty, formally Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, Including the Moon and Other Celestial Bodies, (1967), international treaty binding the parties to use outer space only for peaceful purposes. In June 1966 the United States and the Soviet Union submitted draft treaties on the uses of space to the United Nations.
These were reconciled during several months of negotiation in the Legal Subcommittee of the UN Committee on the Peaceful Uses of Outer Space, and the resulting document was endorsed by the UN General Assembly on Dec. 19, 1966, and opened for signature on Jan. 27, 1967. The treaty came into force on Oct. 10, 1967, after being ratified by the United States, the Soviet Union, the United Kingdom, and several other countries.
Under the terms of the treaty, the parties are prohibited from placing nuclear arms or other weapons of mass destruction in orbit, on the Moon, or on other bodies in space. Nations cannot claim sovereignty over the Moon or other celestial bodies. Nations are responsible for their activities in space, are liable for any damage caused by objects launched into space from their territory, and are bound to assist astronauts in distress. Their space installations and vehicles shall be open, on a reciprocal basis, to representatives of other countries, and all parties agree to conduct outer-space activities openly and in accordance with international law.
As of June 2019, 109 countries are parties to the treaty, while another 23 have signed the treaty but have not completed ratification. In addition, Taiwan, which is currently recognized by 14 UN member states, ratified the treaty prior to the United Nations General Assembly's vote to transfer China's seat to the People's Republic of China (PRC) in 1971.
Among the Outer Space Treaty's main points are that it prohibits the placing of nuclear weapons in space, it limits the use of the Moon and all other celestial bodies to peaceful purposes only, and establishes that space shall be free for exploration and use by all nations, but that no nation may claim sovereignty of outer space or any celestial body. The Outer Space Treaty does not ban military activities within space, military space forces, or the weaponization of space, with the exception of the placement of weapons of mass destruction in space.
The Outer Space Treaty represents the basic legal framework of international space law. Among its principles, it bars states party to the treaty from placing weapons of mass destruction in Earth orbit, installing them on the Moon or any other celestial body, or otherwise stationing them in outer space. —Britannica