The Outer Space Treaty comes into force.

The Outer Space Treaty, formally known as the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies, is an international agreement that establishes the fundamental principles of space law. It was opened for signature on 27 January 1967 in Washington, London, and Moscow, and entered into force on 10 October 1967. The treaty emerged during the Cold War, when the United States and the Soviet Union were competing for supremacy in space exploration. Growing concerns about the potential militarisation of space, particularly the deployment of nuclear weapons in orbit, prompted international efforts to establish rules governing activities beyond Earth. Building upon earlier United Nations resolutions, the treaty was negotiated through the UN Committee on the Peaceful Uses of Outer Space and became a cornerstone of international cooperation in space exploration.

The treaty establishes several important principles intended to ensure that outer space remains accessible to all nations. It declares that the exploration and use of outer space, including the Moon and other celestial bodies, shall be carried out for the benefit and in the interests of all countries, regardless of their economic or scientific development. No nation may claim sovereignty over outer space or any celestial body, preventing territorial ownership of the Moon, planets, or other extraterrestrial locations. The treaty also prohibits placing nuclear weapons or other weapons of mass destruction in orbit, installing them on celestial bodies, or stationing them in outer space. Furthermore, the Moon and other celestial bodies must be used exclusively for peaceful purposes, with military bases, weapons testing, and military manoeuvres prohibited. Countries are also responsible for their national space activities, including those conducted by private companies, and may be held internationally liable for damage caused by their space objects.

Since its adoption, the Outer Space Treaty has become the foundation of modern international space law, influencing subsequent agreements concerning astronaut rescue, liability for space damage, and the registration of spacecraft. It has helped establish a framework for international cooperation in scientific missions, satellite operations, and human spaceflight, including projects such as the International Space Station. However, technological advances and the increasing involvement of private companies have raised questions about how its provisions should apply to commercial activities, particularly asteroid mining, lunar resource extraction, and the establishment of permanent settlements beyond Earth. The treaty also does not prohibit all military activities in space or the deployment of conventional weapons in orbit, creating challenges as nations develop increasingly sophisticated military space technologies. Despite these limitations, the Outer Space Treaty remains one of the most significant international agreements governing humanity’s activities beyond Earth, reflecting the principle that space exploration should be conducted peacefully and for the benefit of all humankind.