As a Justice Department lawyer defended a policy requiring tens of thousands of asylum seekers to wait in Mexico while their cases are processed, a federal appeals judge reminded the Trump administration attorney that his time was running out, advising him to address an area of "real trouble" in the government's arguments.

"You don't even ask whether they have any kind of fear," Judge William Fletcher of the 9th Circuit Court of Appeals, one of three circuit judges hearing the case on Tuesday in San Francisco, told Scott Stewart, a deputy assistant attorney general.

Fletcher referenced the principle of "non-refoulement," a standard in international law that bars countries from sending asylum seekers to countries where they may face persecution. One of the pillars of the legal challenges to the so-called "Remain in Mexico" policy is that the administration is violating this cornerstone of international refugee law by returning migrants — including families with small children — to dangerous Mexican border cities.

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Under the Migrant Protection Protocols (MPP) program, U.S. officials do not affirmatively ask migrants if they fear going back to Mexico before sending them there. As of this week, the administration has returned more than 50,000 asylum seekers to Mexico under this policy, according to Customs and Border Protection (CBP), the agency that oversees the returns.

The oral arguments before the three-judge panel on Tuesday represented the latest phase of litigation surrounding the MPP program since the same circuit court last spring delayed an injunction by a district judge and allowed the administration to implement the policy while the merits of the legal challenges to it are reviewed.

On Tuesday, the plaintiffs, a group of immigrant advocacy groups represented by the American Civil Liberties Union (ACLU), asked the panel to uphold the injunction a judge in San Francisco made in April and to prevent the administration from continuing to implement the policy.

People attend a church service at the Agape World Mission shelter, where many Central American and Mexican migrants stay while trying to reach the U.S. or to request asylum, in Tijuana, Mexico, on Thursday, September 12, 2019. Emilio Espejel / AP

When Stewart defended the practice of not asking migrants placed in this program whether they fear persecution in Mexico as "reasonable," Fletcher quickly interjected.

"But you're giving them nothing," he told Stewart. "That is to say, you're not even asking them the key question with respect to refoulement: that is to say, 'Are you afraid?'"

The Justice Department lawyer suggested migrants could simply inform U.S. officials of any fear they have about staying in Mexico — even if they are not specifically asked. "Purportedly these plaintiffs are asylum seekers who are, at least according to their claims, fleeing persecution and have fears, including in Mexico," Stewart said. "It would be logical for them and the agency can reasonably conclude that they would volunteer their harm."

But Fletcher remained unconvinced by Stewart's argument. "Do you have anything other than speculation to support that?" he asked the government lawyer.

"It's the logic of the provision," Stewart responded.

"But I'm asking about the real world," Fletcher countered before asking Stewart for evidence that demonstrates people would volunteer that kind of information without being asked for it.

After apprehending or encountering them, CBP officials are typically supposed to ask migrants if they fear returning to where they came from. If migrants say yes, they are then referred to undergo so-called "credible fear interviews" with asylum officers, who work for U.S. Citizenship and Immigration Services (USCIS). If the migrants pass the credible fear test, they can formally apply for asylum in the immigration court system.

Migrants placed in the "Remain in Mexico" policy, however, are automatically allowed to apply for asylum. But asylum officers still determine whether they will be sent back to Mexico. A migrant subject to the policy needs to say — without being asked — if he or she fears persecution in Mexico. But advocates say this is something migrants from Central American and other countries in the region are unlikely to do since they may not expect to face persecution in Mexico, having been in the country relatively briefly during their journey to the U.S.

Even if the migrants spontaneously indicate they fear persecution in Mexico, it is almost impossible for them to pass the non-refoulement interviews for the program, according to attorneys and some of the very same asylum officers conducting the screenings.

In the courtroom on Tuesday, Stewart defended the procedures in place for the MPP program, saying the U.S. is returning migrants to "liberty" in Mexico, not to the country they are "claiming to flee." He said the current practice of officials not asking migrants whether they fear returning to Mexico deters what he called "false positives" and claims by migrants who he suggested simply wanted to stay in the U.S. and be released.

As Stewart started to explain that he believed the policy in place stemmed from a "logical conclusion," Fletcher reiterated his skepticism.

"You keep coming back to logical. You don't really have much in the record, do you?" the judge asked.

"Again, your honor, this is a facial— " Stewart said before being interrupted by Fletcher.

"So, the answer is yes — you don't have much in the record," Fletcher said.