It's an interesting issue. The right to move around freely seems more appealing than expecting people to be essentially imprisoned in their countries of citizenship. On the other hand, there are obviously billions of people living in poor and otherwise dis-functional countries, and if even a fraction decided to move to a country like New Zealand, you can imaging it becoming ridiculously overpopulated.

Alternatively, should we accept that population groups that have a higher birth rate should naturally dominate future generations, or is it acceptable to fence off certain parts of the world with lower birth rates and a better natural environment?