The military use of outer space has been integral to national security strategies since the space age began, almost 50 years ago. Recent developments in technology and military doctrine have led to states’ being increasingly interested in deploying weapons in space. An assessment of the situation in terms of international law is therefore necessary. Contrary to common belief, the arms control provisions of the 1967 Outer Space Treaty reserve only celestial bodies for peaceful purposes’: it thus limits military activities in the space between them - outer void space – only in respect of prohibiting weapons of mass destruction applying general international law, including the UN Charter. But force application by space weaponry challenges the regime governing the use of force in international relations, jus ad bellum. First, the concept of force needs to be revisited. Second, the differentiated regimes of outer void space and celestial bodies have a significant impact on the lawful exercise of the right of self-defence, including the deployment of spatial missile defence shields. Thus I shall explore a possible jus in bello spatiale. Military activity in space is likely to increase in wars to come. We therefore need a framework for applying the norms of international law in outer space.
