American Express, Visa, and Mastercard have received a warning from 24 Republican attorneys general.
regarding the application of a distinctive identifier that would identify purchases made at gun stores.
A new merchant rule for gun shops has prompted 24 attorneys general to threaten legal action.
The International Organization for Standardization recently decided to establish the code, and this action is in response to that decision.
All three credit card companies recently announced that the standard had been adopted.
For retailers of guns and ammunition, American Express and Mastercard have adopted a new merchant category code.