Are any chemical weapons legal to use in war? for example tear gas? Is tear gas even considered a chemical weapon?
Depends on who you ask. Before the ground assualt began a newsie was saying the military was told NOT to use CS (tear gas). My SWAG was some people would use that use as an excuse to use badder stuff on US.
I believe that any chemical used to maim or kill people during a war is considered a WMD and therefore illegal. This prevents countries from using pesticides or herbicides that are legal on people. (Agent Orange used in Vietnam was a herbicide).
I should add that to my knowledge, Agent Orange WAS used to defoliate the trees, and as an unintended consequence caused poisoning to humans. I don’t know how to make the neat little cites, but this is a good page about the history of chemical weapons:
www.geocities.com/CapeCanaveral/Lab/4239/chemweapons/history.html