Why does the European Union insist on ‘free movement’?

Nonsense, Crook replies. “This position makes no substantive sense. The indivisibility of the four freedoms is a mere assertion — a preference, not a requirement of fairness or logic.”

It’s a point I hadn’t thought of and it’s indisputably true: you can rip down tariffs and trade barriers and still not allow foreigners to immigrate into your country. This is basically what the United States did in the 20 years after World War II.

So where does “freedom of movement” come from? At the time the Common Market was created, in 1957, Europe was seeing mass migration from Italy and Spain to the richer North, especially Germany. A similar movement was going on within the United States, as one-third of American blacks moved from the South to the North between 1940 to 1965, along with similar numbers of whites from the low-income South to the higher-income North. Farm-to-factory migration, you could call it. And this was also a period of rapid economic growth in the United States and in Continental Europe.

In that setting the idea came naturally to the architects of what became the European Union that labor mobility enhanced, or perhaps was even necessary to, the operation of free markets. You had to allow people to offer their labor where there was a demand rather than remain in places where there was an oversupply. In the United States they could move without crossing international boundaries. In Europe they could move if the EU guaranteed open borders and freedom of migration.

But within both the United States and Europe the south-to-north migration pretty much stopped around 1965. Low-income areas and farmlands where many fewer hands were needed to bring in crops had mostly emptied out. Birth rates fell sharply from what were the baby boom years in the U.S. and much of Western Europe. America’s new migrants would come, thanks to the unanticipated effects of the 1965 immigration law, from Mexico and other parts of Latin America and from various parts of Asia. Europe’s migrants would come from the Muslim world — huge numbers of Turks to Germany, Moroccans to Belgium, Algerians to France, etc.

In recent years domestic migration within the United States has tapered off, for reasons no one seems to fully understand, and net immigration from Mexico has sharply tapered off, to zero from 2008 to 2014 according to the Pew Hispanic Center. Immigration from other places has fallen and immigrants from Asia now outnumber those from Latin America. In Europe, there has been relatively little movement across land national borders but a considerable movement to Britain — the proverbial Polish plumbers, French investment bankers, economically non-productive Roma from Eastern Europe. Resentment of such movement, of the British government’s inability under EU to control it, contributed to Brexit’s victory in the June 23 referendum.

In additional, Merkel’s decision in August 2015, a decision taken unilaterally without consultation with other EU governments, to welcome some 1 million alleged refugees to enter Germany clearly weighed on voters’ minds. Merkel’s humanitarian motives, perhaps resulting from her upbringing in Eastern Germany with its notoriously uncrossable western border, got her named Time’s Person of the Year. But the enormous flood of apparently unassimilable Muslims into Germany — the proportionate equivalent would be allowing 4 million into the United States—seems reckless, and if and when they or their children can become citizens the right of “free movement” would allow them to live in Britain any time they want. You don’t have to be a racist to see this as a threat to the British way of life.

Britain must now negotiate a new relationship with the European Union. Crook points to a solution that would be entirely rational — Britain remains within the free trade area but can control its borders — but which unfortunately seems unlikely to be acceptable to the EU.