Kroger, Walgreens, Walmart and Wegmans are among the retailers that have announced they no longer want customers to display firearms in their aisles, following the Aug. 3 murder of 22 people at an El Paso, Texas, Walmart and some other shootings. But they are still trying to figure out how they are going to put that into practice, representatives told Bloomberg.

“We’re actively engaging with peers across our industry as we work to formulate best practices that will be communicated to our store teams,” said Keith Dailey, a Kroger spokesman, speaking to Bloomberg. “We have asked store management to continue managing our stores as they always have, by prioritizing the safety of our associates and customers.”

Complicating matters for retailers and other businesses is opposition from some organizations and customers, who resent being asked to leave their firearms at home, arguing that the Second Amendment protects their right to carry.

Walmart is not asking its hourly staffers to approach any armed customers, but is instead leaving that to the managers and security personnel, according to someone familiar with the policy, as quoted in Bloomberg.

Still, all employees need instruction on how to approach such situations, says Katherine Schweit, a former FBI agent who is now a security consultant and who has worked with Walgreens, Walmart and others.

“Security training is essential for all employees, whether they are management, a guy in the warehouse, or a person at the cash register,” she told Bloomberg. “But it has to be tailored to the position that person is in. It is obviously a difficult challenge, but certainly not impossible.”