Flame throwers aren't allowed in war but hey how about using small explosives to bomb people's hands/arms away? And that without knowing where this will happen because those people using them could be anywhere when it happens. They could drive their kid to school, sit in a bus or stay on a supermarket cashier so that there is absolutely no way you even try to prevent that many good people will also lose their eyes or something else...
And this will change absolutely nothing to the positive. If at least this would be the goal but it obviously isn't.