Quoting myself for continuity
@TigerGrowls @GesterHawk @baltimorened
I did a little more digging while having my first cup of coffee this morning to provide some additonal context/amplification of my previous post., if interested.
The US made extensive use of riot control agents (CS primarily) in Vietnam. (CS is stronger than what police used at the time) Various delivery menthods. Deliver to an area to force troops out of dug in politions for immediate follow up with conventional weapons to kill them in the open. Pump into tunnel complexes to force the enemy out etc. Cyrstal form of CS was also used for area denial. Similarly it was used to enhance the deterrent effect of diretional mines, by taping bags of CS powder to them, when used for that purpose by small ground elements being pursued and trying to break contact.
US also made extensive use of herbicides ("agent orange") (google operation RANCH HAND ... ran from 1962-1971 employing 19M gallons of various "Raninbow" herbicides (orange, blue, white, purple, orange II/III) (per AI)
The international community took the position that the US was violating the 1925 protocol, which the US had not ratified to date. The US took the position that the protocol only applied to lethal chemical weapons. There was a UN resolution in 1969 combined with domestic unrest that led tu the US scaling back use as our participation in the war came to a close. In 1975 we finally ratified the 1925 protocol and accepted the expanded definition in the 1969 UN resolution.
(P.S. Ned, i know you know the vietnam history... you lived it!)