MIAMI — It was early December, and Monroe County Sheriff Rick Ramsay had had it with the federal government’s response to what he considered a “humanitarian crisis” as more and more migrants arrived by boat in the Florida Keys. “The mass migration is depleting critical staff from doing their assigned duties of protecting, responding, investigating and patrolling our communities,” he said at the time. Every day, it seemed, more and more people, usually from Cuba and sometimes from Haiti, arrived in overloaded boats. Ramsay’s 203 road patrol deputies lacked the jurisdiction to do much more than ...