This International law has prohibited the use of chemical weapons since 1899, under the Hague Convention: Article 23 of the Regulations Respecting the Laws and Customs of War on Land adopted by the First Hague Conference “especially” prohibited employing “poison and poisoned arms”; also, a separate Declaration stated that in any war between signatory powers, the parties would abstain from using projectiles “the object of which is the diffusion of asphyxiating or deleterious gases.
