Hey, why should they care about Belgian or any other national laws? Islam tells them slavery is Ok as long as they are enslaving infidels, so the local laws don’t matter.
Gosh, maybe they should just jet over to the UK, with that “Separate but more than equal” Sharia thing about to start going on there.
OTOH, there have been many, many incidents of turd world servants kept as might-as-well-be slaves by the rich. Even the not so rich. It’s really only a step or two past what goes on here with all the illegal alien workers at the chicken processing plants, etc.