If you’ve been reading this blog, you probably know the basic moral and economic (is that different?) arguments for open borders. In short: Immigration restrictions actively harm people by prohibiting them from making beneficial trades. They appear to be horrifically inefficient, causing a deadweight loss on the order of 100% of world product. So, restrictionists have a rather heavy burden of proof.

One of the putative downsides of open borders is that immigrants might cause crime. According to this argument, immigrants are statically more likely to commit various crimes than domestic citizens, and for that reason, it is justifiable to exclude.

One response to this argument is to dispute the empirical claims. In fact, empirical studies generally find that immigrants are less likely to commit crime than domestic-born citizens. Bas van der Vossen and I will summarize the studies in our forthcoming book with Oxford. I’m not bothering to link to them here, though, because I want to ask, instead, what if immigrants did in fact cause more crime? What if immigrants were more likely to be criminals than the domestic population? Would that be sufficient reason to restrict international migration?

Consider a parallel with internal migration. Suppose DC starts having so many problems that the poor blacks living in Anacostia and Ward 8 start trying to move to Northern Virginia. Now, suppose the governments of Arlington, Alexandria, Falls Church, and Fairfax County say, “We must protect our citizens from crime. Accordingly, we are closing off borders with Washington, DC. We will forbid immigrants from DC.” Would that be just? (I’m not asking if it’s legal–obviously, it’s not–I’m asking if it’s just.)

Most people would think this is an unjust, evil, racist policy, even though it gets the facts right. (Yes, poor blacks living in Ward 8 in DC are statistically more likely to commit most sorts of crime than the current residents of Northern Virginia.)

But if they think it’s unjust to restrict internal migration because of crime, but not international migration because of crime, this shows that this putative justification for border controls–“We can close borders to protect our citizens from crime”–isn’t doing independent work. Rather, it shows they already have some other reason for thinking it’s permissible to interfere with would-be external immigrants but impermissible to interfere with internal immigrants.

Of course, this is just one argument among many. The point here is just the the crime argument, even if it had the facts right, wouldn’t do to the work people need it to do.