Unfortunately your juridical skills are too limited to compete with me. So once again here just for you: You have to make a difference between private sales and commercial sales. If you're doing it in a commercial style, especially regularly dealing with new weapons and thousand rounds of ammunition as Steven Steiner alias BayAreaCoins is doing it, you need two things: A license on federal level called FFL, and a locally registered trade business. I won't cite the legal text for you, go ahead and study it for yourself!
Please, you have to give up this petty obsession with BayAreaCoins. You are threatening reporting him for violation of gun sales laws? Why? That has nothing to do with anything, least of all you. If you really insist on reporting this user to law enforcement, then just do it. No need to give us updates about it. His activity isn't hurting anybody. Find an instance where he actually scammed somebody, that would be much more interesting.