Senate Democrats are appealing directly to gun retailers in a renewed push to expand background checks in lieu of congressional action on the divisive issue.

Gun safety advocates in Congress have long called for lawmakers to close background check loopholes that allow criminals to buy guns online and at gun shows, but to little avail.

Now, they’re turning their attention to gun retailers such as Cabelas and Bass Pro Shops in hopes of convincing them to tighten their policies. They’re asking these stores to voluntarily refrain from selling guns to people who have not passed background checks.

“That’s a voluntary decision by the gun dealers,” Sen. Richard Blumenthal (D-Conn.) told reporters Tuesday. “It’s a voluntary decision to enable a killer; it’s a voluntary choice to empower a murder.”

Blumenthal was speaking at a gun safety press conference hosted by Everytown for Gun Safety and Moms Demand Action for Gun Sense in America.

At issue are existing regulations that allow people to purchase guns at retail stores without completing a background check.

These stores must submit information about prospective gun buyers to the FBI so it can run background checks on them before the sale is made. In many cases, the background checks are instant and the sale is made on the spot. But sometimes it takes longer to complete.

If the FBI does not respond within three days, the store is allowed to move forward and make the sale. According to Everytown, more than 15,000 dangerous people have obtained gun through this loophole over the last five years.

Gun safety advocates are calling on stores to voluntarily refrain from selling firearms to what they say is a small fraction of people who have not completed an FBI background check.

This marks a change in strategy for gun safety advocates. They have long pressed for lawmakers to strengthen background checks, but amid a gridlocked Congress they are now turning their pleas to industry.

Some have already listened. Wal-Mart, Sports Authority, Dick’s Sporting Goods, Dunham Sports, Academy Sports & Outdoors and Big 5 Sporting Goods, for instance, only sell guns to people after the FBI has completed their background check and approved the sale, according to Everytown.

“Why not do as Walmart has done?” Blumenthal asked. “Insist that there be a background check before you sell the gun.”

“That’s something every gun retailer could do this week at no consequence to their bottom line,” added Sen. Chris Murphy (D-Conn.), who also spoke at the press conference.