Anyone with a metal lathe can also manufacture a completely untraceable firearm. So perhaps because there's a small chance that someone will do that, then use that firearm to injure another person all metal lathes need to be serialized, registered and tracked.
Or anyone that can buy pipe. All pipes must herefor be sold only after a full background check since it is possible to fill a pipe with explosives and blow up large numbers of people.
Liquid chlorine bleach and ammonia will require 40 hours of intensive training before you may purchase either item, otherwise someone could mix the two and poison an entire building of people.
People killing other people is a social problem. No technology or law will stop it. If making things illegal stopped crime then we would not need the police to clean up after all this crime!