Why are they worried about the NSA?
Every major on-line retailer today is using Visa Level 3 data
What is Level 3 data?
From the Visa web page:
Level I and II data elements plus
Item unit of measure
Item commodity code
Item product code
Item unit cost
Item VAT tax amount/rate
Very easy to make a list of all the item product codes that are firearms-related. Very easy to figure out from descriptions.
Visa already has a huge database of all gun-related buyers.