The most insane thing about this is that it is not illegal to manufacture firearms in the United States. Providing that you do not sell or distribute the firearm, it is entirely legal to manufacture a firearm in the USA for personal use only. Laws vary state by state, of course, and it may be different in the state of New York, but assuming that this federal law has not been overridden by some state law in New York, then this proposed regulation is 100% nonsensical.