Which agreement banned the use, production and destruction of chemical weapons and the stockpiles?

The Chemical Weapons Convention (CWC) is an arms control treaty which outlaws the production, stockpiling, and use of chemical weapons and their precursors. The full name of the treaty is the Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on their Destruction and it is administered by the Organisation for the Prohibition of Chemical Weapons (OPCW). The treaty entered into force in 1997. The parties' main obligation under the convention is to prohibit the use and production of chemical weapons, as well as the destruction of all current chemical weapons. The destruction activities are verified by the OPCW.

As of October 2015, about 90% of the world's declared stockpile of chemical weapons had been destroyed. The convention has provisions for systematic evaluation of chemical production facilities, as well as for investigations of allegations of use and production of chemical weapons based on intelligence of other state parties