Would allowing tear-gas and other "chemical weapons" in war break down what we consider war? Would it somehow lead to wars so brutal no one would want to wage t

Would allowing tear-gas and other "chemical weapons" in war break down what we consider war? Would it somehow lead to wars so brutal no one would want to wage them? How desperate does a relatively sane country have to get before it deploys tactics we would currently reserve as "terrorism" and "weapons of mass destruction"?