There’s an issue with the logic of it being a war crime making it bad. It seems to make sense, but it’s ignoring the reasons for it. The reason you can’t use tear gas in warfare is because your enemy doesn’t know if it’s tear gas or mustard gas (until it hits). If you see gas rolling across the battlefield then you’re likely to deploy your own where you can too. It leads to escalation. It’s the same reason why you shouldn’t point a fake gun at someone with a real gun; you’re probably just going to get yourself shot.

This is still bad. It shows how hostile they’re willing to be. They’re making people feel pain (at minimum, and often it’s much worse) for no good reason. It’s literally terrorism. It’s state sponsored, so that word won’t be used, but when you’re using violence for political gain, that’s the definition.