“Suppose Marvin is in danger of starvation and walks to the market to buy some food. In the absence of outside interference, the market is open, and there are people willing to trade him food. Now suppose I block Marvin from reaching the market. As a result, he starves to death. In this situation, I would surely be said to have killed Marvin, or at least done something morally comparable to killing him.

Countries are like the market where would-be immigrants could satisfy their needs. There are people willing to hire immigrants, to rent them living spaces, and in general to engage in all other kinds of interactions with them. Governments actively and coercively prevent many from meeting their needs that they would otherwise. This is much closer to inflicting a harm than it is to merely allow a harm to occur.”

— Michael Huemer, Starving Marvin (Open Borders: The Case)