Not entirely true. An FFL holder must comply with the laws of the state that he is licensed in, plus the laws of the buyers home state. Sometimes that is not possible. Such as, I'm in Alaska, where we don't have any state restrictions for sales, but if my buyer is from a state that runs their own background checks, or has a state mandated waiting period, or some other convoluted state hoo-hah, then it's not possible for me to do that. The buyer is "out of luck" in that case, regardless if it is a long gun. Military service members that are PCS to the state are viewed as defacto residents and get a pass, regardless of their home state.