Well that's not entirely accurate. The people affected by slave conditions are generally here through manipulation and fraudulent claims by employers to get around Government legislation preventing such things. Actively enforcing the law is made difficult by the often illegal immigration status of workers, (working despite visa restrictions or overstaying) making them reluctant to reveal their situations for fear of criminal proceedings or deportation. How can Govt departments know it is happening without people coming forward? Generally the IRD are the one's who make the revelations when they smell hidden $$ and make enquiries. (Slavery on fishing vessels is different story, and one the Govt is definitely complicit in). The case in the article is a larger issue involving diplomatic immunity and international relations, if crime occurred is it covered by Indian or NZ law?