Chemical Weapons Convention
The Chemical Weapons Convention is a treaty by several members of the United Nations. It calls on its signers to pledge never to use chemical weapons in warfare, and to destroy any stocks of chemical weapons they have. It also calls for strict regulation on the making of any chemical that anyone could weaponize.
The Organization for the Prohibition of Chemical Weapons administers the Convention and all regulations that follow from it.
This Convention does not directly call on any State party to take up arms against another State party, or a non-signer of the Convention, under any circumstances. At most it calls for referring "situations of sufficient gravity" to the United Nations Security Council.