CEUTA, Aug. 16 -- He was 25 years old, Sudanese, and had been crouching in the hills outside Fnideq for the better part of two days. Three miles away, across a fence and a customs post, lay the Spanish enclave of Ceuta, and beyond it, continental Europe. When asked why he was trying to reach it, he said: "In Ceuta, in Europe, people are better cared for. There's no work here. There's no money."

Early on Saturday morning, Morocco made sure he could not get there.

Moroccan security forces arrested 294 people who had gathered near the Castillejos area, southwest of Ceuta, ahead of a mass crossing attempt organized openly on social media. Forty-six of those arrested were Moroccan nationals; the remainder had come from sub-Saharan Africa. Th...