Donald Trump's Mexican border wall has been a rallying cry and all-purpose metaphor since his improbable campaign began in 2015. But if and when it gets built, the wall would also be, well, a wall. The U.S. president's decision Tuesday to let the so-called DACA program expire is aimed at pushing Congress to find a permanent legislative solution to the question of children of undocumented immigrants already on American soil. It would be the beginning of the nuts and bolts (and bricks) of the Administration's on-the-ground plans for overhauling immigration policy. The Washington Post reports that Trump may aim to link a deal to allow current undocumented residents to stay to the funding of the wall along the border with Mexico meant to keep others from arriving.

Across the Atlantic, the issue of immigration has its own dynamic and geography — and imagery. For more than a decade, we have gotten used to desperate scenes of would-be migrants trying to make it across the Mediterranean from North Africa in rafts and small fishing boats, too often dying along the way. Then in 2015, rather than rafts or walls, Hungary had its fences instead: makeshift barriers erected to keep out a new wave of refugees from the war in Syria trying to cross onto European Union territory.

Not a one-way street

On Wednesday, the metaphor of those fences got its day in court. The European Union's top tribunal rejected a challenge by Hungary and several other Eastern European countries to fixed quotas for each EU country to take in a certain number of refugees. Still, it remains unclear what will happen on the ground. In Hungary, where ardent anti-immigration Prime Minister Viktor Orban continues to take a hard line, not a single refugee has received asylum since the crisis peaked two years ago.

European Parliament President Antonio Tajani was quoted by Italian daily La Stampa as saying that relocation procedures must begin now, with penalties imposed on the countries that don't comply. "Solidarity," he quipped, "is not a one-way street."

There has been another recurring plotline in the global migration saga in recent years: the so-called "Jungle" in Calais, France, where thousands of migrants from continental Europe have gathered to try to pass into Britain from across the English Channel. A year ago, French authorities decided it was finally time to dismantle the makeshift village once and for all, forcing migrants to locations elsewhere in France.

Le Figaro reports that, little-by-little, migrants have begun to return to Calais. A few dozen have grown to a few hundred in the past weeks, still hoping to make it into the UK where job prospects are better. It is a reminder that the metaphors of migration are ultimately a very human question of mathematics.

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