From what I understand, they have the containment policy, meaning brothels are illegal but police let them operate as long as they follow legal business procedures. But when the police want to be arseholes, they are more than happy to bust brothels as promoting prostitution etc etc....
I dont see the illegality of the sex industry. Brothels provide a service like your local lawn-mowing man or beauty parlour. The people who work there choose to do so and are normal human beings like everyone else with families, mortgages and kids.