"To disperse protesters, police have also used tear gas, a chemical weapon that’s banned in war — but is technically legal for law enforcement to use during demonstrations. Over the past few days, police have deployed the chemical in Dallas, Los Angeles, New York City, Minneapolis, and even cities with significantly smaller gatherings."
https://www.thecut.com/2020/06/tear-gas-is-a-chemical-weapon-why-can-cops-use-it.html
"As police officers across the country have tear-gassed crowds in attempts to disperse protesters, claims have surfaced on social media that tear gas is a chemical weapon banned in war but legal for law enforcement purposes."
https://www.usatoday.com/story/news/factcheck/2020/06/06/fact-check-its-true-tear-gas-chemical-weapon-banned-war/3156448001/
"As the United States dispenses tear gas at the southern border, trying to deter migrants from crossing over into the U.S., there has been a lot of talk about whether or not tear gas is actually a chemical weapon. Many right-wing pundits, commentators and Twitter trolls have been claiming that tear gas “is not a chemical weapon”."
https://hillreporter.com/fact-check-is-tear-gas-a-chemical-weapon-15567
"Riot control agents (sometimes referred to as “tear gas”) are chemical compounds that temporarily make people unable to function by causing irritation to the eyes, mouth, throat, lungs, and skin."
https://www.poynter.org/reporting-editing/2020/there-are-many-types-of-tear-gas-heres-how-to-tell-the-difference/
Tear gas and pepper spray are chemical weapons. So, why can police use them?
https://theconversation.com/tear-gas-and-pepper-spray-are-chemical-weapons-so-why-can-police-use-them-140364