It's a hard one to teach, because everything carries so much baggage. Comparative advantage as they teach it is not a bad idea. It's a long road from that premise to the conclusion that free markets are all you need to know about humans.

Migrant workers have been for thousands of years and still are, the most powerless class of people. They have no political power, almost by definition. The levels of minimum standards protection they get make a big difference.

I think this is an area that the UN could have done something about, but never did.