It’s not the shipping laws it is the sales laws. Companies are not supposed to sell "used ammo" because they don't know what happened to it. They quote federal law saying that they must sell only ammo loaded by a licensed loader, so if you are not licensed then they can't sell ammo they got from you. I as well don't sell ammo that comes in second hand unless I specify that I got it from an Individual and it is at their own risk. I do get it from other dealers and licensed loaders as well as wholesalers. Insurance is a whole other matter.