This publication explores the concept of common security and the legal foundations for its application in outer space law, based on the premise that outer space is an internationalised common area beyond the national jurisdiction of individual states, and therefore security in space must be the common security of all states. Chapters cover a range of issues including: the principle of the peaceful use of outer space, passive military uses, and multilateral negotiations to prevent an arms race in outer space; structural change of international law and the common heritage of mankind principle; and proposals for a multilateral agreement and the creation of an International Organisation for Common Security in Outer Space.