We are talking about the difference between permission and legality. A bar won't let you bring in outside drinks because they want to make more money. That doesn't imply anything about legal culpability. I've got other posts here about profit if you want to go around-and-around on that one.
Let me give an example: I get a Wendy's hamburger, walk over to DQ, sit down and start eating. The nail concealed within the burger drives through the roof of my mouth, into my brain, and kills me. (I bite down hard) What judge in their right mind is going to hold DQ responsible, and let Wendy's go scott-free, for killing me?
If simple presence within an establishment indicates responsibility, then any business could make itself invulnerable to responsibility simply by providing nowhere for customers to sit down. (Like a coffee stand or hot-dog vendor)
If you can come up with a local statute or precedent from an official source, or I'd even settle for a news article from a reliable source where a business was held legally responsible for a problem with outside food in a court of law, then I will say "Okay, I was wrong" and happily let it drop. It's not possible for me to prove the absence of a law. Until then, we could just go around and around with "Yup" and "Nope" and, as you said, it's getting rather boring.
And so far you have called me an ass, and implied stupidity with your shoe comment. Don't try to escape responsibility for your insults. You aren't a restaurant.