The Maastricht Treaty, the 1992 agreement about currency, citizenship and freedom of movement on which the present European Union is built, was drafted for a world that was disappearing. Back then, only a handful of richer countries — France, Germany, Britain, and the Netherlands among them — had significant immigration, and already majorities were unhappy with it. These countries were industrial powerhouses, with economies structured to favor workers and benefits that were envied around the world. They had big militaries, which they no longer seemed to need now that the Cold War was…
