One of the reasons that banks did away with armed guards was the court rulings that no business has a responsibility to protect its customers or employees from outside ( non-employee) armed attack. No business must protect you from outside attack. Think about it. The police do not have to protect you from attack (USSC Decisions) they have only to investigate after the attack and arrest culprits, if they find any. "Serve and Protect" is an empty motto. Given, cops die every day trying to do just that and every
LEO I know considers it his duty to protect the public. But there is no
legal requirement for them to do so. You cannot sue the police for not protecting you! ( That may be a surprise to many!)If you cannot hold the police responsible for your protection , how could you hold a business responsible? The only thing
they can get in trouble with is something harming you because of
their actions or negligence in following established ordnances.
If a bad guy shoots you in an establishment, you cannot charge them because they let him in, you have to charge the BG.
At least this is the Criminal Law. I am sure everybody is aware that Civil law lets you sue for anything you want. You may even win a lawsuit against the BG's third grade teacher because she didn't teach him better manners, if the jury is crazy enough to go along with it. (There is no rhyme or reason, nor boundaries, to civil law! You cannot possibly cover all of the bases for civil law, it depends on what the jurors were smoking or sniffing that morning. If I sound skeptical, I've served on three civil trial juries and they were zoos!)