WASHINGTON — Asylum seekers may be turned away without a hearing at the southern border, the Supreme Court ruled Thursday in a historic retreat from the promise of relief for those who say they are fleeing persecution. The justices split over whether this was a simple dispute over legal wording or a moral question involving desperate families. Siding with the Trump administration, the court’s conservatives said the Refugee Act of 1980 offers a right to seek asylum to migrants who “arrive in the United States” but not those who are turned back when they approach a border crossing or a port of...