After facing mounting pressure from Democrats and anti-gun activists, credit card giants Visa, Mastercard, and American Express all announced plans this week to single out their customers’ purchases at firearm stores. Using a new four-digit merchant category code, credit card companies will now categorize any purchases at gun ammunition stores, regardless if those purchases are of firearms or not, as separate from other shopping. If the credit card companies deem any of those transactions suspect, they will report them to local law enforcement agencies. Visa, Mastercard, and AmEx all adopted the new standards on Saturday shortly after the International Organization...