In September, the International Organization for Standardization (ISO) had launched a Merchant Category Code (MCC) for gun retailers. ISO is the organization responsible for classification of merchant categories used by payment cards. Discover told Reuters that it plans to implement the code beginning April. "We remain focused on continuing to protect and support lawful purchases on our network while protecting the privacy of cardholders," the company said.

Discover's decision has attracted strong criticism online. "This is a MASSIVE problem Congress needs to address, IMMEDIATELY!" Lauren Boebert (R-Colo.) said in a March 3 tweet.

"Discover Card will begin tracking firearm purchases starting next month. There are more than 50 million Discover cards in use right now. They are coming for your guns little by little," Congressman Troy E. Nehls (R-Texas) said in a March 3 tweet.

"It's called a Social Credit System. I have been warning ppl this is coming. This is just the tip of the iceberg," said radio host Doll Arntzen.

Social Credit System is a national credit rating system used by Beijing that ranks and blacklists people in China based on criteria approved by the communist regime.

"American citizens should be able to exercise their Second Amendment rights without fear of being tracked or discrimination against. We're solving this in West Virginia with the Second Amendment Financial Privacy Act. Congress needs to follow our lead," said Riley Moore (R-W.Va.) in a tweet.

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