27 more countries need to ratify the Treaty on the Prohibition of Nuclear Weapons (TPNW) for it to come into force. 50 states need to not only sign the treaty, but ratify it (in democracies, this usually requires parliament to pass a law).
The first three countries to ratify the TPNW were Guyana, Thailand and the Vatican (all on 20 September 2017).
The other ratifiers are (in chronological order): Mexico, Cuba, Palestine, Venezuela, Palau, Austria, Vietnam, Costa Rica,…