On 4 June, the Bulletin of the Atomic Scientists carried an article pointing out that, unlike the tactical gear and military vehicles US police often employ, tear gas is not even allowed on actual battlefields. It goes on to say that, just as it is not legal to shell an opposing army with sarin or mustard gas, it is also illegal to fire off commonly used riot control agents such as chloroacetophenone (CN) and chlorobenzylidenemalononitrile (CS) in war. Law enforcement use of so-called riot control agents (RCA) is not prohibited by the Chemical Weapons Convention. However, the article says that some weapons researchers think the law enforcement exception in the Chemical Weapons Convention was a mistake. Unlike well-known chemical weapons like sarin, chlorine, and mustard gas, RCA are not intended to kill or cause serious injury, but that does not mean law-enforcement chemicals are safe.
If you would like to say thanks by making a small contribution, in case I need to upgrade or replace my computers and other paraphernalia, I have a page at https://www.buymeacoffee.com/KoIvM842y