I fail to understand how in anyway a customer should involve themselves in a situation of underage, abuse or forced work at a licensed establishment. For that matter, aside from a condo or such, involve themselves with business license. Of course you could be faced with a situation and you choose whether to get involved or not, in my case LE warned me if I got involved too much with the males involved I could find myself in harms way ( I didn't even blink ).
So to the OP, if you are visiting a licensed establishment you should have a reasonable expectation that the girls are there because they want to be and are of age. If you are visiting a spa where extras are common, the likelyhood of LE activity increases, to what degree, I can't say.