One of the largest banks in the United States has just announced it will no longer do business with any client who doesn’t abide by it’s new rules on selling firearms.

Citigroup posted a letter on its website this week, declaring its clients must not sell firearms to anyone who hasn’t passed a background check, and must not sell firearms to anyone under 21 years of age. It also prohibits the sale of bump stocks of high-capacity magazines. Any client who does not accept the new rules will have to find a new bank.

President Trump announced on Twitter on Friday that he was issuing a ban on all all sales of bump stocks.

The Citigroup mandate, written by Ed Skyler, Executive Vice President of Global Public Affairs, wrote of the recent mass shootings, and said something must change.

Below is a portion of the announcement:

Today, our CEO announced Citi is instituting a new U.S. Commercial Firearms Policy. It is not centered on an ideological mission to rid the world of firearms. That is not what we seek. There are millions of Americans who use firearms for recreational and other legitimate purposes, and we respect their Constitutional right to do so.

But we want to do our part as a company to prevent firearms from getting into the wrong hands. So our new policy centers around current firearms sales best practices that will guide those we do business with as a firm.

Under this new policy, we will require new retail sector clients or partners to adhere to these best practices: (1) they don’t sell firearms to someone who hasn’t passed a background check, (2) they restrict the sale of firearms for individuals under 21 years of age, and (3) they don’t sell bump stocks or high-capacity magazines. This policy will apply across the firm, including to small business, commercial and institutional clients, as well as credit card partners, whether co-brand or private label. It doesn’t impact the ability of consumers to use their Citi cards at merchants of their choice.

We know our clients also care about these issues and we have begun to engage with them in the hope that they will adopt these best practices over the coming months. If they opt not to, we will respect their decision and work with them to transition their business away from Citi.

We have few relationships with companies that manufacture firearms. For those that do, we will be initiating due diligence conversations on the subject to better understand what products they make, what markets and retailers they sell to and what sales practices those retailers follow to ensure adherence to the best practices outlined above. This same due diligence screening will apply to potential clients going forward.

These common-sense sales practices already have widespread public support according to recent polling and they are easy to implement. Some, like Walmart, have gone even further.