Justice Elena Kagan said the second provision was meant to be discretionary because another country was affected.
“Congress, aware that Mexico is a sovereign nation, did not think it appropriate to say, ‘You must ship people back to Mexico,’” she said. “It understood that there was going to have to be discretion and significant foreign policy considerations involved in that choice.”
A third provision allows the government to release migrants into the United States while they await their hearings “on a case-by-case basis for urgent humanitarian reasons or significant public benefit.” Ms. Prelogar said the government used that provision for tens of thousands of migrants each month.
Justice Samuel A. Alito Jr. questioned whether the government was applying the statutory criteria in more than cursory fashion. Chief Justice Roberts told Ms. Prelogar that “there is no limit, as you read the statute, to the number of people you can release into the United States.”
The liberal justices said the court should be wary of, in effect, conducting foreign policy.
“Judges, this is above your pay grade,” Justice Stephen G. Breyer said. “Stay out of it as much as you can.”
Justice Kagan said federal judges should not be able to order the government to take actions at odds with its diplomatic priorities. “What are we supposed to do?” she asked. “Just drive truckloads of people to Mexico and leave them without negotiating with Mexico?”
Last year, Judge Matthew J. Kacsmaryk of the U.S. District Court for the Northern District of Texas, in Amarillo, ruled that the immigration laws required returning noncitizens seeking asylum to Mexico whenever the government lacked the resources to detain them.