This is still surreal to me, buying guns online with credit card...
For the benefit of people reading this thread from other countries, here is the way it works in the USA.
To receive guns from mail or post you must have a FFL - Federal Firearms License. A person with FFL can receive guns from factory, distributors or other FFL. These guys must adhere to both the federal and state law.
For me as a private citizen to send a gun to a buyer in another state, I would drop it off at the office of a FFL, pay him a small fee like $25USD and the shipping costs. The person buying it from me would go to his designated FFL, pick it up and pay his small fee. At that time that FFL would execute the NICS FBI background check on the receiving individual. Hyatt Gun would have shipped to FFL only. Mail order sales would be expected to be specialty items that were not available locally - this process costs about $100 more than a local dealer sale - although the mail order may not pay local sales tax.
So the story here is that Hyatt Gun - doing everything legally and correctly - ran into a problem where someone in Visa management simply didn't like guns.
There is no story here whatsoever that Visa knew better, or had found a flaw in the system. There MAY BE a story here of propaganda value, that is about it.