Lol love these types of business decrees that literally anybody not conditioned from birth not to question authority wouldn't believe for a second.
This is up there with the signs on dumptrucks that say they aren't liable if so thing flies out of their truck and hits you. You'd literally get laughed out of court if you tried to argue it meant anything but fuck it might ad well try.
I hope somebody shows up to Walmart with a shirt that says "I've instituted a no arrest policy on my self, I believe that any claims of "shoplifting" or "larceny" can be worked out with a reasonable conversation, just lemme run to my car reaalllll quick."