The legality of the possession and use of nuclear weapons has attraced renewed attention in recent times. This is due to a range of factors, including the entry into force of the Treaty on the Prohibition of Nuclear Waepons (TPNW); nuclear sabre-rattling by Russia; the Russian-Chinese campaign to deligitimize the NATO nuclear sharing agreements; the Chinese campaign for a 'No First Use' Treaty; the suspected plans from Moscow to place a nuclear device in outer space, etc. The attention for the topic is bound to increase, i.a. in light of the upcoming 2026 Review Conference of the Non-Proliferation Treaty, and the attempts from some corners to request a new Advisory Opinion from the International Court of Justice on the legality of nuclear weapons (in the wake of the highly controversion Opinion of 1996). The project aims to offer a critical and comprehensive international legal analysis of the developments in the field since the start of the 21st century.