The status of nuclear deterrence under international law in light of the Treaty on the Prohibition of Nuclear Weapons

Abstract

Nuclear deterrence is not illegal under international law but is being delegitimised, in part as a result of the adoption of the United Nations Treaty on the Prohibition of Nuclear Weapons. The Treaty prohibits not only possession, control over, threat of use, and use of nuclear weapons or other nuclear explosive devices; it also precludes a state party from encouraging and assisting anyone to engage in such prohibited activities. Moreover, artificial intelligence, offensive cyber operations, and enhanced non-nuclear weapons with strategic impact are combining to render nuclear deterrents ineffective while greatly increasing the risks of unintended or accidental use. Conflict in February 2019 between two nuclear-armed states, India and Pakistan, has shown the dangers and frailties of nuclear deterrence. Nonetheless, nuclear-armed states are engaging in major nuclear weapon modernisation programmes, resulting in a new nuclear arms race. This new race is characterised by the development and deployment of hypersonic missiles containing multiple independently targetable warheads as well as by variable-yield nuclear weapons. Nuclear disarmament, which was negotiated by statesmen at the height of the Cold War, is urgently needed.