A federal judge on Friday sharply questioned the Biden administration’s position that it bears no responsibility for housing and feeding migrant children while they wait in makeshift camps along the U.S-Mexico border.

The Border Patrol does not dispute the conditions at the camps, where migrants wait under open skies or sometimes in tents or structures made of tree branches while short on food and water. The migrants, who crossed the border illegally, are waiting there for Border Patrol agents to arrest and process them. The question is whether they are in legal custody.

That would start a 72-hour limit on how long children can be held and require emergency medical services and guarantees of physical safety, among other things.

U.S. District Judge Dolly Gee said evidence presented by migrant advocacy groups appeared to support the definition of legal custody. “Are they free to leave?” she asked.

“As long as they do not proceed further into the United States,” answered Justice Department attorney Fizza Batool.