Legally, whether something is a "chemical weapon" depends on whether it's used to attack people, or is used in population centers where many people will be dire

Legally, whether something is a "chemical weapon" depends on whether it's used to attack people, or is used in population centers where many people will be directly injured regardless of intent. See also the legal wrangling around US use of white phosphorous, which is 100% legal if used as an "illuminant" [https://treaties.unoda.org/t/ccwc_p3 https://treaties.unoda.org/t/ccwc_p3] (i.e. for flares), but not as a weapon against people.