Missile Defence Shields: Automated and Anticipatory Self-Defence?

In response to the escalating rhetoric and bellicose actions emanating from the Korean peninsula in April 2013, the United States deployed Patriot Missile Systems at its overseas military bases in danger of being struck by a North Korean missile launch. Japan took similar precautionary measures. A more permanent fixture and fitting in terms of Missile Defence Systems (MDS) is Israel’s Iron Dome Shield—designed to intercept rocket attacks by Hamas militants albeit more so for strategic benefit and less so for defending the civilian population. Both defence shields / systems, however, are designed for the same purpose—to intercept missile attacks during the ‘free flight’ phase (noting that this is specifically used in the ‘Ballistic Missile Defence context’). This article examines whether use of missile defence shields help support the existence of a wider right of anticipatory self-defence. The article also addresses the point at which an‘automated’ response takes place. Does such a response fall within the barometers of necessity and proportionality that govern a state’s lawful recourse to self-defence under international law?