Tear gas is a riot control agent and is considered as chemical weapon under Chemical Weapon Convention if used in warfare.

“Riot Control Agent” means: Any chemical not listed in a Schedule, which can produce rapidly in humans sensory irritation or disabling physical effects which disappear within a short time following termination of exposure.

Countries can possess and use riot control agents including tear gas for domestic law enforcement. However, countries must declare to Chemical Weapon Convention (CWC) the type of riot agents they possess. Article 1.5 of CWC says “Each State Party undertakes not to use riot control agents as a method of warfare”

Classification criteria of IMDG Code states “Tear gas substances shall be included in packing group II even if their toxicity data correspond to packing group III values.”

List of tear gas entries in IMDG Code