seeing as how i worked the sporting goods counter at wally world for 5 years i will chime in. Many, if not all, states have their own laws that specifically say where residents can and cannot purchase longguns.
I'll use Kentucky as my example since I know their state law off the top of my head.
a resident of the state of kentucky may only buy a firearm in states that are contiguous to kentucky ie:Ky, Tn, Mo, Il, In, Oh, WV, and Virginia. If you are a resident of kentucky those are the only states, according to kentucky state law, that you can purchase firearms in.
the only non-residents that can purchase firearms in the state of kentucky are from the same states listed above, according to Ky state law. a person from florida cannot purchase a gun in Ky because florida is not contiguous to kentucky.
clear as mud right? i'm sure Arkansas has a similar law that specifically says who(non-resident-wise) that can purchase long guns there. there are many dealers that do not either know this or don't abide by it. I worked the sporting goods counter for about 3.5 years before i discovered it one boring evening while flipping through the different states laws in a gun law book we had.