Indeed there are. Exploding, mushrooming, and other bullets that cause "unnecessary harm and suffering" are not banned under international treaty. Oddly enough, silencers and flash suppressors are also restricted, and I have no idea why. That's why we need one of those microwave guns fast. Just wholesale cook the bastards.
Can you just imagine a laser type weapon where the "deadly force" from the weapon hits the target INSTANTLY, and in a perfect straight line?! That would be truly amazing. And we may just get something like it relatively soon.
But a quick death prevents both. Having several neat, .22 or .30 cal holes punched through you OTOH, IS needless pain, harm, & suffering.
Don't some of "them" also bitch about the use of .50BMG against a person with a rifle on this same ground; or, at least on grounds of "disproportionate" force?
It's the enemy, stupid; kill them quick and in overwhelming numbers, by any means at hand, until they all die or quit.