By Kristina Cooke and Mica Rosenberg (Reuters) -U.S. authorities were blocked by a federal judge on Friday from lifting COVID-19 restrictions that empower agents at the U.S.-Mexico border to turn back migrants without giving them a chance to seek asylum. The nationwide injunction issued by U.S. District Judge Robert Summerhays in Louisiana means the restrictions, which were set to end on May 23, will remain in place across the border as the litigation proceeds, unless a higher court overturns the ruling. The Department of Justice (DOJ) said it intends to appeal. The pandemic restrictions, know…