Despite slavery being illegal, the UK decided that a lease treaty for a small part HK meant they had the right to gift the citizens of one of their territories to another country. The lease covered the land but the hand back treated the people as transferable chattels.
Unfortunately, the rights of these people are somewhat protected by am wink-nod law that expires when the current generation of youngsters will be too old to fight. The glorious mainland government has been finding ways to improve this stupid law earlier and guarantee state jobs for the police. If Hong Kong sounds like a great place to raise your children, please consider joining police force.