i doubt that "weird powdery stuff" would have much of an effect. if its only strong enough to knock the wind out of a normal person i don't think it would help against someone trying to attack you. i've been punched in the stomach before it was a really strong hit and it knocked the wind out of me, but i was still standing and managed to keep up the fight sustaining multiple blows like that. sometimes lethal force is the only option. plus if guns become illegal then your gonna have a real pissed of public who would die for their freedom to bear arms.