Today's NYT has an op-ed against China's one-child policy. There is no doubt that it is a very great restriction on human freedom, but in my mind it is also the most successful economic and political policy of all time. The institution of the one-child policy played a key role in the explosive growth of the Chinese economy over the past several decades and turned it from one of the poorest countries in the world into an almost wealthy superpower.
It would be ridiculous to argue that there haven't been some bad side effects, but I suspect that it looks a lot like the future. Either people will voluntarily choose to have few children or that choice must be made for them. Probably one of the fairest ways to encourage low population growth is to tax children. Of course in countries with too rapidly falling population, opposite incentives are appropriate.