Except anarchists, I think "Randians" and most "free market advocates" are in favor of court (government) enforcement of contracts.
> He was 16
There's a concept of "age of consent" or "capacity" to contract.
> arranging a fake passport stating he was 20
Fraud.
> wages retained
Who would sign a contract like this? It's most likely a violation.
> deprived of the ID cards they need to move around freely without fear of arrest
Seems like a failure of the State, to be arresting people who are allowed to be there.
> demand their wages, a drastic step given that the authorities can simply expel them to penury
If "the authorities" refers to the State, I'd say it's another failure of government, not the free market.
> refusing to issue the exit permits they needed to return home
Yet another failure of the State, if I'm reading that correctly as a restriction of the freedom of movement: a basic human right which brutal, anti-capitalist regimes are infamous for violating (e.g. Berlin Wall). Historically, people tend to flee from less free (market) countries to more free (market) countries.
> the kafala system binds the worker to a single employer
Is "kafala" a system of laws? This sounds like Directive 10-289 which Ayn Rand rails against in Atlas Shrugged: "All workers, wage earners, and employees of any kind whatsoever shall henceforth be attached to their jobs and shall not leave nor be dismissed nor change employment"