Only libertarians advocate completely free movement, writes Will Wilkinson, yet there is much to be said for a degree of openness in immigration policy

In recent months American Republicans have taken to labelling their Democratic Party rivals as advocates of “open borders”. Stephen Miller, a top White House aide, complains that Democrats have resisted expanding immigrant prison camps for kids “as part of their crusade for open borders”. Steve King, a hardline anti-immigration congressman from Iowa, maintains that Americans “face an identity crisis, as open-borders politicians are seeking to ‘fundamentally transform’ our nation through mass immigration policies". And then, of course, there is President Donald Trump. “The Democrats are for open borders, which means crime,” Mr Trump recently opined. “It's not a question of, like, what do you think it means. Open borders means crime.”

You may not be shocked to learn that Mr Trump inverts the truth. Democrats are not principled advocates of open borders and free movement. Immigrants are less likely to commit crimes than native-born Americans. And there is definitely a question of what “open borders” means.

What does it mean for borders, and immigration policy generally, to be open? Once we clear the air of Trump-like demagoguery, open borders can be seen as one tool among many in the moderate, liberal immigration-policy kit.

Out of the mouths of Messrs King, Miller and Trump, “border” basically means “the purity of the national stock” and “open” basically means “defilement.” “If we don't have borders,” Mr Trump has said, “we don’t have a country.” As it happens, America does have borders, and is a country. What Mr Trump means, and what his supporters hear, is that a country is a people of a unified ethnicity, and a drift towards a different, more varied complexion must be stopped.

This confusion of immigration policy for demographic social engineering has led Mr Trump to split up families, jail toddlers and terrorise immigrant communities.

But it is important to see that demographic change is only incidentally a matter of “borders”. If ethno-nationalist population control is the policy goal, then the presence of an already large multicultural population and declining white birth rates are bigger obstacles than immigration.

And a country can have no immigration restrictions and no immigration if no one wants to go there. Conversely, a country can outlaw all immigration, spend lavishly on “border security”, yet nevertheless find itself with a high rate of unauthorised migration, especially if nearby countries are impoverished or shattered by war.

In this heated debate, America could learn from a rather surprising example: the European Union. Poland and Romania have open borders with more than 20 other EU countries, yet non-nationals from the EU make up only 0.6% and 0.9% of their respective populations. Spain has open borders with its neighbours France and Portugal. Yet there are six times as many Moroccan residents in Spain (who have often entered the country illegally), than there are from France or Portugal, despite relatively aggressive Spanish measures to deter boatloads of North Africans arriving on their shores. This shows that if a country is wealthier, more peaceful and freer than its neighbours, it can expect to receive a steady flow of people migrating, legally or not, towards better prospects.

As the EU makes plain, the notion of “open borders” is not all or nothing. Legal entry and residency can be open to citizens of some countries but not to others. The French are free to waltz into Spain, but Moroccans aren’t. Moreover, it is a mistake to conflate a permissive immigration policy with “open borders”, since selective openness is compatible with overall restrictiveness. A border that is entirely open to the citizens of a few nearby countries can be, on the whole, less porous than one than that is open to anyone anywhere who ticks the right boxes. Immigration policy can’t shut down streams of human traffic. Instead, free and prosperous liberal societies require clear rules that respect and regulate inevitable migration flows.

It is illuminating to consider America’s chief immigration “problem” in this light. The southern border reflects the annexation of previously Mexican territory. The United States is wealthier than Mexico. America depends heavily on Mexican labour. But it has made family unification, or “chain migration”, the only broadly available legal route into the country.

The rate of unauthorised immigration from Mexico has been steadily declining for more than a decade, in part because of economic convergence, and in part because more aggressive border enforcement has encouraged people who would otherwise go back and forth to hunker down with their families on American soil.

An open border between Mexico and America, on the model of the open border between Spain and France, could fix the problem. It would bring peaceful and productive labour migration within the rule of law, reduce exploitation and abuse by employers and human smugglers, and more speedily shrink the gap in living standards that, more than anything, draws Mexicans north.

(However, opening the border with Mexico would not solve the Central American refugee crisis. Nor is it an answer to the question of whether to recast the immigration policy on merit-based rather than family-based migration, or whether it is better to issue more visas or fewer.)

Aside from a handful of libertarian idealists, no one is proposing to open borders everywhere to everyone. But to defend the existing liberal order is to stand up for multicultural societies. And according to Gallup, a record high 75% of Americans now say immigration is a good thing. This shift in opinion, should it last, could open up new opportunities for liberalising immigration reform. A sane debate is impossible, however, if the public mind continues to be polluted by nativist misdirection.

Will Wilkinson is the vice-president for research at the Niskanen Center and a contributor to the New York Times