For starters, the U.S. Postal Service will not mail handguns. Only contract or common carriers (UPS or FedEx) are by law authorized to ship handguns. UPS will not ship a gun from a non-licensed individual to another non-licensed individual. They require shipments of guns to either originate or terminate with a holder of a federal firearms license. You must disclose to UPS that you are shipping a gun. FedEx will also not ship a gun from a non-licensed individual to another non-licensed individual. Just as with UPS, the firearm shipment, at a bare minimum, must either originate or terminate with an FFL. You must disclose to FedEx that you are shipping a firearm.

So no, it’s illegal for violent felons to purchase guns, and online sales and shipping require the involvement of a federal firearm license holder and the use of background checks.