In an essay on “The Great Brexit Breakdown” (Wall Street Journal, December 7, 2018), Gerard Baker quotes the director of a London-based think-tank: “You can have national sovereignty—and that’s fine. Or you can have economic integration—and that’s fine. But you can’t have both,” says Mr. Grant. This is true if “national sovereignty” means that the national government has the right to control its subjects’ decisions to become integrated to the world economy, that is, to import to from or exporting...