I'm not disagreeing with you, but I've seen several people buy, sell, and trade guns in gun stores. I've also seen employees of gun stores sell their personal guns to people in the store after going outside to make the transaction outside of the business and taking off or covering anything that associated them with the shop.
If this is illegal, I've never seen it enforced nor heard of it.... I suspect it's a Matt Eastman style rule to make the people buy from the dealers and not each other. I can imagine why it would be legal for me to sell my gun to someone in a daycare center but not in gun store.
