Prohibits use of new merchant category code by credit card companies for purchases of firearms and ammunitions.

New Jersey's S 1866 prohibits credit card companies and financial institutions from using a new International Organization for Standardization merchant category code specifically for firearm and ammunition retailers. The bill requires these retailers to be classified under standard codes for general merchandise or sporting goods instead of a separate "firearms" category. This prevents payment processors from flagging or tracking firearm purchases through credit card transactions. The law aims to stop financial institutions from creating de facto gun registries or chilling Second Amendment rights by restricting how transaction data is categorized. It applies directly to firearm retailers and payment processing entities in New Jersey.