If they refuse to take them back Trump can hit them with tariffs, that already worked once.
It might work in Mexico, but what about the Salvadorans, Hondurans, and Guatemalans, not to mention all the other places where these immigrants might be from. Ike was working with a ready and willing country. I see legal complications and diplomatic complications dragging out for months and months. Meanwhile, we are now probably paying to hold people in custody as the courts grind out the legalities of forcing unwilling countries to take back people they probably don’t want anyway. Here is an idea, while holding them teach them how to fight against vicious gangs and their own gangster politicians, and arm them with weapons, pamphlets, cell phones, and computers so they can foment revolution at home and improve the conditions that are encouraging so many to flee to the US. Maybe not weapons, but the rest.