The relationship between ius ad bellum and ius in bello

Abstract

The rules of international law governing the legality of the use of force by states (ius ad bellum) and the rales by which international law regulates the actual conduct of hostilities once the use of force has begun (ius in bello) have seldom sat happily together. In the immediate aftermath of the Second World War, some international lawyers took the view that the development of the ius ad bellum by the Charter of the United Nations had rendered the ius in bello superfluous. This view has, not surprisingly, become somewhat less fashionable of late and the four Geneva Conventions of 1949, the 1977 Protocols to those Conventions, and a number of other treaties bear witness to the continuing interest of the international community in regulating the conduct of warfare. Nevertheless, the suspicion remains that ius in bello should have been absorbed by ius ad bellum, that the two subjects are somehow in competition, so that discussion of the former distracts attention from the more fundamental requirements of the latter or implies a lack of confidence in it. Thus, one letter published in The Times at the height of the Falklands conflict castigated international lawyers for engaging in a debate about the law concerning the treatment of prisoners of war on the ground that they should have been devoting their attention to questioning the legality of the whole operation mounted by the United Kingdom.