One has to be careful when making an argument for closing borders. The problem is that many of the arguments people offer lead to conclusions they are not prepared to endorse.

The arguments for closing borders appear not just to be arguments for closing borders, but for censorship, voting restrictions, eugenics, internal migration restrictions, and more. Or, if they’re not, closed border advocates rarely show us why not.

Closing borders is in the first instance a form of economic protectionism. When we close borders, we forbid people from making willing, mutually-beneficial trades with one another. At first glance, it looks like we’re violating a right of freedom of movement and a right of freedom of association.

Perhaps such restrictions can be justified, but we need a good reason. But now look at the reasons people give, and ask whether these reasons imply not merely that we should close borders, but that we may do a whole host of other illiberal things. Consider:

We need to close borders to maintain a liberal culture. If you think so, then to maintain a liberal culture, you should also in principle be willing to censor certain points of view, or forbid or ban certain religions. You might also favor forced indoctrination into liberal ideas.

We need to maintain our distinctive culture. Again, if that’s a good reason to close borders, why is it not also a good reason to censor certain ideas, ban certain forms of music, or ban certain religions? Why not mandate that people support and participate in certain cultural practices? Why not require people to speak certain languages at home, or read certain books?

We need to prevent domestic wages from falling. If so, would you (if the facts turned out the right way) also forbid women from entering certain jobs?

Immigrants won’t vote the right way. If you find that persuasive, then in principle you should be open to forbidding certain parties, banning certain people from voting, or engaging in political censorship.

Immigrants will cause crime. Isn’t this also an argument for eugenics or for internal migration restrictions? For instance, should New Hampshire ban young black men from Washington, DC [statistically more likely to commit crime than the average New Hampshirite] from moving there? If banning rap music reduced crime, would you favor that?

Immigrants will eat up the welfare state or consume too many public goods. Is this not also an argument for restricting births, or forbidding internal migration, or even requiring some people to give birth?

We have a right to self-determination, and we may choose to exclude people. Is this not also an argument that “we” may choose to exclude some people from having children?

We collectively own our institutions and may exclude people, or dictate the terms on which they associate with us. If so, doesn’t this also license us to do pretty much whatever we want, including censoring people, forbidding some from having children, and so on?

Now, perhaps the defender of immigration restrictions can come up with plausible accounts of why immigration restrictions are permissible, but then explain why they are not committed (at least in principle) to these other illiberal policies.

But one thing I’ve noticed, when reading the various arguments philosophers and others have put forward for immigration restrictions, is that they almost never bother to explain why not. They make broad arguments that have scary implications, arguments that do not specifically show that we may close borders, but arguments that, if sound, imply all sorts of illiberal things. But the authors of these arguments just don’t notice where their arguments lead.

Consider how Paul Collier might respond. He thinks that, as a matter of fact, banning certain immigrants would help prevent an illiberal culture from forming. He might respond that, given the facts, we don’t need to censor people, indoctrinate them, or ban certain religions. He might be right.

But we can still ask him, “Would you in principle be willing to do those things, if the facts were different? If, e.g., allowing people to convert to Islam turned out to be just as dangerous as you think allowing immigrants from Afghanistan, would you favor banning Islam, in order to maintain a liberal culture committed to the rule of law?” I doubt he’d say yes.

A version of this post first appeared at Bleeding Heart Libertarians.