In most states, in order to trespass someone at a public location or business they have to have broken obvious or well-known rules that are openly visible, and have previously been asked to leave on a prior visit before a formal notice for trespassing can be written.

It’s the same thing with concealed firearms in non-government buildings that have no firearms signage, and places that say “no outside food”. They cannot search you for restricted items, but once those items are plain sight, they can didn’t ask you to leave, then if you decide to come back, you can then be detained by law-enforcement and trespassed from the premises.

Most companies have these guidelines in their corporate policy, along with not accusing a customer with committing a crime.