El Paso has a very colorful history, full of the good, the bad and the ugly. Most cities do but El Paso has been around a minute and one of its markers is the time it was "spitty".
You've seen them and, being unaware of this law as I was, probably didn't even bat an eyelash. Although, you may have raised an eyebrow. They are blatant about it, almost intentionally trying to draw attention to their flagrant lawlessness.
The laws regarding alcohol in Texas are complicated and there's a buttload of 'em. Here are at least two you probably break every time you raise a glass.