Like it or not, the Treaty on the Prohibition of Nuclear Weapons enters into force today. It is the first treaty that comprehensively prohibits nuclear weapons. Critics of the ban treaty say that the TPNW “would neither make nuclear weapons illegal nor lead to the elimination of even a single nuclear weapon”, and they are right because the nuclear weapons ban campaign had a different goal. It is a norm change campaign that makes a crucial step towards the abandonment of the old norm of nuclear deterrence and the practice it supports.