AUDIE CORNISH, HOST:

A U.S. immigration policy upheld by the Supreme Court last night forced a big decision in Mexico today around the migrant protection protocols. It's also known as the "Remain in Mexico" policy. The U.S. procedure forces asylum-seekers to live in Mexico - and according to immigration activists, in dangerous conditions - while waiting for a court hearing in the U.S. Reporter James Frederick joins us from Mexico City to talk more.

Welcome back, James.

JAMES FREDRICK, BYLINE: Hi, Audie.

CORNISH: I want to start with some background about how the "Remain in Mexico" policy had been working.

FREDRICK: So as you mentioned, this was a Trump-era policy, but Biden ended it almost immediately after his inauguration. It affected about 71,000 people, most of them from Central America or Cuba. Basically, a person would show up at the U.S.-Mexico border and say, I'm in danger. I want to request asylum. They'd be taken into the U.S., processed, and then turned around and sent back to Mexico with a court date in a U.S. court. And they'd have to wait there, outside of the U.S., until their asylum process was finished, which could take years. These people, again, were not Mexican, and most of them did not know the country at all. In theory, the Mexican government gave these people humanitarian support. But in reality, that didn't happen, so thousands of people ended up living in really dire makeshift camps along the border.

CORNISH: What had the policy been trying to accomplish?

FREDRICK: The Trump administration was very clear about it. They wanted to deter people from requesting asylum, and this would make the asylum process much harder, much more difficult. There's no evidence that the policy did stop people from requesting asylum, but there's lots of evidence that it did make things very, very bad for asylum-seekers. The advocacy group Human Rights First documented more than 1,500 cases of kidnapping, rape and murder of people under this program.

Here's how Omar Jadwat, the director of the American Civil Liberty Union's Immigrant Rights Project, described the situation for asylum-seekers under this program.

OMAR JADWAT: They came to the United States. They asked for protection from persecution. And we put them in harm's way, and they suffered as a result.

CORNISH: Harm's way. I mean, how and where does the Mexican government fit into this U.S. policy?

FREDRICK: Well, with the Supreme Court decision, this is a U.S. policy, and that's all the Supreme Court was talking about - was about a U.S. law. But if the U.S. is going to send asylum-seekers back into Mexico, Mexico has to agree to that. They can say no. So here's Jadwat from the ACLU again.

JADWAT: If Mexico says no, then the program can't restart. You know, it's that simple. The U.S. government is required to make a good faith effort.

FREDRICK: So what he's referring to there at the end is the Supreme Court telling the Biden administration that they have to make a good faith effort to restart this program. So in theory, they could ask Mexico to restart it. Mexico could say no. And the Biden administration can turn around to the Supreme Court and say, we made efforts, but it's not possible because of Mexico. So in theory, the policy could die right there.

CORNISH: So what have you learned about what the Mexican government has said about all this so far?

FREDRICK: The Mexican government has been very tight-lipped about this so far. They did acknowledge that they know about the decision. They have been in contact with their U.S. counterparts, but they said they have not made a decision yet. It's important to mention that Mexico's president, Andres Manuel Lopez Obrador, agreed to this program back in 2019. And in general, he's really gone along with U.S. immigration policy, even under President Trump. He even deployed military forces to detain migrants here. So Mexico generally is not hostile to U.S. immigration policies. So if Mexico does end up giving the green light to this, and the program restarts, a very bad humanitarian situation at the border right now could get even worse. There are currently migrant camps at the border, very terrible conditions right now because of a different Trump-era policy that Biden has kept in place. And, you know, I saw some of these camps. They were very bad. So if this policy comes back into place, a bad humanitarian situation might get a lot worse.

CORNISH: That's reporter James Frederick from Mexico City.

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