The question before the judges — two appointed by President Bill Clinton and one by President Ronald Reagan — is whether the policies should be in effect while lawsuits proceed. They did not rule immediately.
Judge William A. Fletcher, a Clinton appointee, told a Justice Department lawyer that the administration may be "in real trouble" because immigration authorities don't ask asylum seekers if they fear being sent back to Mexico. The lawyer, Scott Stewart, responded that they can express fears on their own initiative, which didn't satisfy the judge.
"Do you have any evidence of any sort that tells you that you're going to get a high percentage of people volunteering that information?" Fletcher asked, concluding after some back and forth that the administration had none.
ACLU attorney Judy Rabinovitz pressed for additional steps before an asylum seeker is sent back to Mexico, including rights to consult an attorney or have a translator.
Backers of the policy, known officially as "Migrant Protection Protocols and colloquially as "Remain in Mexico," say it prevents asylum seekers from being released in the United States with notices to appear in court, which they consider a major incentive for more people to come. Its expansion coincided with a sharp drop in Border Patrol arrests from a 13-year-high in May.
Opponents say it has exposed asylum seekers to extremely dangerous conditions in violent Mexican border cities while they wait for court hearings. Human Rights First, and advocacy group that has criticized the policy, issued a report Tuesday that said there were more than 340 public reports of rape, kidnapping, torture and other violent crimes against asylum seekers who have been sent back.
The asylum ban on anyone who crosses the border illegally from Mexico also drew pointed questions, including whether it violated U.S. law that says it doesn't matter how people enter the country.
Trump and Roberts clashed last year after the president denounced a judge who ruled against him on the ban as an "Obama judge." Roberts said there was no such thing in a strongly worded statement contradicting Trump and defending judicial independence. Trump defended his own comment, tweeting defiantly, "Sorry Justice Roberts."
The Supreme Court ruled in Trump's favor last month by letting another asylum ban take effect, denying it to anyone who passes through another country on the way to the U.S. border with Mexico without first applying there.
This story has been corrected to show the spat between Trump and Roberts predated the Supreme Court ruling.