During the Trump administration, US border agents were directed to separate detained migrants from their children. That produced an outcry. Under Biden, border agents have been photographed using horses to charge at migrants trying to cross the border. That too has an produced outcry. But if these measures are wrong, which measures a permissible? After all, few people think the border restrictions can never be justified no matter what the circumstances. How then should borders be enforced? Mollie Gerver from the University of Essex has tried to identify the relevant moral principles. And she's done something else as well, something philosophers rarely do: empirical research to find out whether the public agree with her.

Mollie Gerver is a Lecturer in Political Theory at the University of Essex. She is the author of the The Ethics and Practice of Refugee Repatriation. The article we discuss is not yet published, but if you are interested, please follow @molliegerver or @kieranoberman on Twitter and we will link to it once it is out.

Cover art by Raphael Perez.