While China's one-child-per-family policy is usually seen as an internal affair, there are any number of reasons why it should not be regarded that way.
The biggest immediate result of this policy is female infanticide on a vast scale - to the tune of maybe 100 million female fetuses aborted. This is not only a crime against humanity; it is also dangerous. 100 million unattached males in one country means, in the worst case scenario, another world war. Which means that other countries have a stake in changing this policy.
A much more humane, and much more realistic, policy would be two children per family. That would mean replacement rate. It would also mean fewer female infanticides and fewer unattached males. China, with its stellar economic growth, can afford more than one child per family. Whereas the population growth rates are the greatest in places that can least afford them.
Would the unattached Chinese males go for women by conquering poorer countries in Africa and South and Southeast Asia? Would they create a vast military that would try to conquer the world? Would they cause riots and ugly scenes of violence? This is a real problem for China; it is also a real problem for the rest of the world.
And then of course there is a matter of, well, what happens if a child dies? If a family is kept to one child per family scenario, then that would mean the family line dying out. Parents would have felt like they had worked all their lives for nothing. And that would cause a major possibility of all sorts of protest and instability.
Efforts to control population growth are in many cases appropriate. But one child per family policy in a vastly growing economy is overkill, and it is also dangerous for reasons stated above. There need to be more efforts to that effect in Africa; and it is there, not in China, that we see people multiplying without a chance at their children having a future.
This policy needs to be re-evaluated. Vast numbers of unattached men is dangerous for everyone; and one child a family policy is simply inhumane. Don't go the way of Africa and practice reckless reproduction, but don't be cruel to your people either. A two-child per family policy would work a lot better. It would mean replacement rate; and it would also reduce the dangerous situation of the country having vast numbers of unattached males.