Why is the legality of using nuclear weapons under international law debated?

The debate regarding the legality of using nuclear weapons under international law is complex, as there is no single, universally accepted consensus on whether their use is per se illegal.

While international humanitarian law strictly regulates the conduct of war—prohibiting weapons that cause unnecessary suffering or fail to distinguish between combatants and civilians—the application of these principles to nuclear weapons remains a subject of significant controversy.1

The core of the legal debate centers on whether the catastrophic and indiscriminate nature of nuclear weapons can ever be reconciled with the fundamental requirements of necessity and proportionality. Proponents of a ban argue that the inherent characteristics of nuclear weapons make it impossible to use them in compliance with humanitarian standards. Conversely, some states maintain that their use could be permissible under specific circumstances, such as in the exercise of the inherent right to self-defense when a state's survival is at stake.1

Ultimately, while various treaties like the Treaty on the Non-Proliferation of Nuclear Weapons aim to curb the spread of these arms, they do not explicitly restrict their use in time of war.23