Let's just pretend the government implements a law that demands all citizens to forfeit their assault rifles. Let's pretend, after this law is implemented, that the penalty of not forfeiting your assault rifle is 15 years in prison if an assault rifle is discovered to be in your possession. Then, let's consider the crime we would be trying to prevent: Mass Murder. Now, let's consider the much harsher penalty that is already implemented regarding first degree murder: Up to life in prison or the death sentence. So, we must ask ourselves, "Should we be under some impression that a person who would disregard a punishment of life in prison would respect a law that could risk them 15 years in prison?" Mass killers take drastic measures to wreak havoc. Obtaining an illegal weapon would not be such a surprising law for them to break.