The Outer Space Treaty of 1967 and its companions are silent on the matter. In the future the regimes of ‘space’ and ‘air-space’ may well be delineated similarly to the distinction that is made between the high seas and other areas of the sea subject to national sovereignty, but as authors write there is uncertainty – not that space law exists, but as to the exact location of its application. Of course the absolute rule of sovereignty had to be modified at least between the parties to permit ease of commerce, but the default position was sovereignty. In the ultimate a state is entitled to enforce its sovereignty, as an exercise of that sovereignty, by shooting down an unauthorised intruder. Sovereignty in the air-space was a functional rather than a territorial concept, a state controlling what is done in the ‘air-space’ rather than being ‘sovereign’ in the way it is sovereign over its physical territory.