Credit card giants Visa, Mastercard and American Express are taking steps to help better track firearm sales in a move hailed by gun control proponents.

Why it matters: Payment processors have been under pressure to help monitor gun purchases amid concerns over mass shootings and other violence.

What's happening: A panel of the International Organization for Standardization voted to approve the creation of a "merchant category code" (MCC) for gun retailers — and the credit card companies are adopting the change.

Supporters hailed the development as a critical step toward undermining the flow of guns into the hands of violent people.

Yes, but: The manner in which the code is used may determine whether it's effective in bolstering monitoring efforts, goes too far or doesn't go far enough.

The other side: Opponents warned that the move sets a dangerous precedent, potentially opening the door for additional tracking of other types of transactions.

The big question: How will the credit card companies — which are steeped in fraud detection — determine whether a purchase from a gun store is suspicious?

The bottom line: Financial companies are getting more proactive in an effort to show they're not ignoring fears about guns.