In July 2021, Amalgamated Bank petitioned the International Standards Organization (ISO), which sets standards for the financial industry, to create a new merchant category for firearm and ammunitions sellers. A new merchant category would help credit card companies track purchasing patterns for firearms and ammunitions and potentially flag suspicious activity, such as purchasing large amounts of weapons at different stores. Amalgamated Bank noted that this information would help financial institutions provide information to law enforcement agencies that could be used to prevent crimes such as mass shootings.

The ISO denied Amalgamated Bank's petition, and in February 2022 denied Amalgamated Bank's appeal of the decision. Documents obtained by CBS News indicate that employees from American Express, MasterCard, and Visa sat on an internal ISO committee that recommended the rejection. The ISO told CBS News that the employees advised the committee in a personal capacity and "do not represent the views of their employer."

American Express and Mastercard said they were working to ensure only lawful purchases were permitted on their networks in a statement to CBS News. Visa declined to comment.

In August 2022, officials from New York and California pension funds joined the call for credit card companies to create a new merchant category to track gun purchases.

Business & Human Rights Resource Centre requested a response from American Express, MasterCard, and Visa regarding the allegations that they blocked reform efforts to help credit card companies flag suspicious gun purchases and prevent gun violence. MasterCard responded; American Express and Visa did not respond.