Major credit card companies are moving to make a merchant code available for firearm and ammunition retailers in order to comply with a new California law that will allow banks to potentially track suspicious gun purchases and report them to law enforcement, CBS News has learned.

Retailers are assigned merchant codes based on the types of goods they sell, and the codes allow banks and credit card companies to detect purchase patterns. Currently gun shops are lumped in with other types of retailers, such as sporting goods stores.

Mastercard, Visa and American Express initially agreed to implement a standalone code for firearm sellers, but later paused their work on it after receiving blowback from Second Amendment advocates concerned tracking gun purchases would infringe on the rights of legal gun owners.