Nuclear weapons in international law
The legality of the threat or use of nuclear weapons was not being assessed when the atomic bomb was developed during the Second World War. Instead, all relevant deliberations had concentrated on how to end that war quickly without considering questions related to the future role of nuclear weaponry. Important rules of international law which inform a professional legal assessment today, including the UN Charter, have entered into force only after the ﬁrst and so far only case when nuclear weapons were used. Furthermore, the role of nuclear weapons has undergone important changes since the end of superpower confrontation during the Cold War, and so have the challenges posed by their existence. Hence any legal assessment must consider the different historic phases for the role of nuclear weapons in military planning and decision-making. Different branches of international law are relevant in this respect. It is in this broader context that the role of states and non-state actors in the development of pertinent principles and rules are to be considered. The present chapter will discuss the role of nuclear weapons in the different phases since their existence and undertake a legal assessment of their use (Section 1). Various achievements towards the legal regulation of nuclear armament will be evaluated (Section 2); and emerging open issues for research and government action in the coming years will be addressed (Section 3). The chapter is not limited to considerations under the law of armed conﬂict; it shows that conclusions to be drawn on the current role of nuclear weapons and their legal regulation in the contemporary world requires an assessment of a larger spectrum of issues (Section 4).