The real value of the nuclear ban treaty The book of signatures at the signing ceremony for the Treaty on the Prohibition of Nuclear Weapons, September 20, 2017. UN Photo/Kim Haughton. Last month, 75 years after nuclear weapons were first used, a treaty came into force that bans them. The Treaty on the Prohibition of Nuclear Weapons (TPNW), also known as the ban treaty, is the culmination of a decade of work by civil society leaders and diplomats who, frustrated by stagnation in traditional venues, focused the lens of international humanitarian law on nuclear weapons. This approach, dismissed at first, resonated with many states that understood nuclear weapons to be inherently indiscriminatory and inhumane.