One of my family members is a pharmacist. One of his previous employers (a "big box store") had an "instant termination" policy for carrying a firearm on store property. And, the employee handbook threatened legal action, if the firearm was used on company property (even if preventing injury to employees or self). They claimed that store security (actually pretty good, and armed) was more than enough. ....But didn't escort anyone through the pitch black parking lot, to the distant employee parking area, in a bad part of town, after closing; even if they were making the night deposits at the bank (no armored car service in that area
).
After having to draw his weapon to stop a cashier from being harmed during a robbery, the store manager chose to "look the other way" on the no firearms policy. Some similar incidents around the country have gotten that company to change their policy to something more akin to "don't ask, don't tell; if you use it, we'll sue".