Independent Bar Food Vendors: Good? Bad? Illegal?

A very bright Disher with a mind for springing questions asks for your opinion. Seems he frequents three bars, the names of which I have removed, where independent food vendors enter the establishment and sell barbecue sandwiches, burritos, tamales, and other items. The bartenders don’t seem to mind because they don’t serve food. My first thought is that the selling of food in a public establishment without a catering license is illegal. Here is his initial question.

I’ve noticed a trend in bars that don’t serve food which I’d like to get your opinion on. It’s very common now to see different food vendors walking through places like the XXX, XXX, and XXX selling barbecue, tamales, burritos, etc. On a given night, these vendors will make several passes through these bars and I’ve seen them sell as much as $35 on a single pass. What’s the protocol on this? The bar owners get nothing out of this, the bartenders pay full price for their food and let’s face it, customers who eat more drink less.

Anyone seen this? Dealt with it in your establishment? Love to hear from  you.