Question: When did the united nations ban chemical weapons?
Disambiguated questions and answers: question: When did the united nations ban chemical weapons by calling for all states to strictly observe the Geneva protocol?
When did the united nations ban chemical weapons with the Chemical Weapons Convention signing?
When did the united nations ban chemical weapons with the Chemical Weapons Convention becoming effective?
answer: 1966
13 January 1993
29 April 1997
Natural Questions answer: 1968 (from the Wikipedia article "Chemical Weapons Convention")