“The social equivalent of laws”? Yes, you do start getting blurrier here. What the heck is that? It is against the law but the laws are poorly enforced? How much of a wink wink nudge nudge counts?
I really am not meaning to be difficult. I have honest discomfort over how to define it. Part of me doesn’t see why it matters what the societal norm is or isn’t: if they are held and being used against their will by threat of (or by use of) violence for the purpose of profiting from their labor, and escape is a small possibility at best, then what difference does it make if the society ignores it or is just ignorant of it? The effect is the same. OTOH I can see how the definition can become so broad as to become of little value. A prostitute abused and threatened by her pimp (her keeps almost all the money) to the extent that she is afraid to leave his employ doesn’t seem to me to be the same thing as a slave.
How and where to draw the line is the hard part. Which is why the op did present a debate (even if all he intended was some recreational outrage). I see it as quite blurry indeed. Use your new definition now and take the op’s case as an example even. Within the country of origin keeping these people captive was not legal perhaps but was clearly tolerated. The hotel may even have intentionally looked the other way. Only by virtue of having gone outside their own country and into a society where, outside the hotel at least, the “social equivalent of laws” no longer wink-winked, did the possibility of escape arise. Were they not slaves?