New York (CNN) US credit card giants said they will implement a new merchant category code for the nation's gun retailers, which gun control activists say will help flag potential mass shooters and gun traffickers.
The International Organization for Standardization, based in Geneva, approved the code on Friday. The system will separately categorize sales at gun and ammunition stores, which advocates say can help track suspicious transactions of firearms and ammunition.
Visa, the world's largest payment network, will "proceed with next steps" the company said in a statement Sunday, "while ensuring we protect all legal commerce on the Visa network in accordance with our long-standing rules."
American Express said it will follow its usual business practices and work with third-party processors and partners to implement the code.
"We are focused on ensuring that we have the right controls in place to meet our regulatory and fiduciary responsibilities, as well as prevent illegal activity on our network," the company said in a statement Sunday.
A statement Saturday from Mastercard noted that recent bipartisan action in Congress is a positive step in "meaningfully" addressing gun violence. Now that the ISO approved the new merchant category code, Mastercard said it is turning its focus to how the system will be implemented by merchants and their banks.
"We continue to support lawful purchases on our network while protecting the privacy and decisions of individual cardholders," Mastercard said in a statement. "This is exactly how we would manage the process for any other appropriate MCC, like a bicycle shop or sporting goods store."
Nearly every retail item has a merchant category code — prior to Friday's decision by the ISO, gun store sales were classified under a general merchandise or sporting goods category.
Merchant codes track where a consumer used a credit card, but won't flag what specific items were purchased. Gun rights activists have argued the code would unfairly surveil legal gun purchases.
"This is not about tracking or prevention or any virtuous motivation — it's about creating a national registry of gun owners," the NRA said Sunday.
The New York Times found in 2018 that electronic payments were used to purchase the guns and ammunition used in some of the country's most lethal mass shootings, including in Aurora, Colorado, San Bernardino, California, Orlando, Florida and Las Vegas.
Amalgamated Bank and some politicians, including New York City Mayor Eric Adams and Sen. Elizabeth Warren, had pressured the ISO to implement the code. The financial firm had applied to the ISO for the code for the first time last summer, an Amalgamated official said.
"The new code will allow us to fully comply with our duty to report suspicious activity and illegal gun sales to authorities without blocking or impeding legal gun sales," Priscilla Sims Brown, President and CEO of Amalgamated Bank, said in a press release Friday.