The Trump administration has reportedly found a way to force asylum-seekers to wait in Mexico during the months — or longer — it takes to apply for protection in the US, making the tens of thousands of Central Americans and others who flee northward to the US each year essentially Mexico’s problem to solve.

On Saturday, Nick Miroff and Joshua Partlow of the Washington Post reported that the Donald Trump administration had made a deal with the incoming president of Mexico, Andres Manuel Lopez Obrador, to implement a “Remain in Mexico” policy.

Contemplated since the earliest days of the Trump administration — one of the first executive orders the president signed instructed the Department of Homeland Security to look into the prospect — the policy would bar asylum-seekers from entering the US until their applications were approved (or until they got deported) unless they had a “reasonable fear” of staying in Mexico.

While the two countries are still hammering out the details, it appears that the biggest question — whether Mexico would cooperate — has now been settled.

The appeal to the Trump administration is clear. The administration is desperate to reduce the number of people entering the US without papers to the anomalously-low levels of Donald Trump’s first few months in office — even if it means asylum-seekers face a bevy of human-rights concerns while they remain in Mexico, from criminal victimization to concerns about food and shelter.

The US could start implementing the new policy in the coming days or weeks, likely starting at ports of entry (official border crossings) in San Diego, where thousands of asylum-seekers have been waiting on the other side.

There’s a lot we still don’t know about how this is going to work — either because it hasn’t actually been worked out yet, or because details aren’t yet public. As it stands, this could be a temporary inconvenience — or lead to the US essentially creating refugee camps just across the border. Here’s what we do and don’t know.

What we know about the US/Mexico asylum deal and the “Remain in Mexico” policy

• The Trump administration has negotiated a tentative deal with Andres Manuel Lopez Obrador, or AMLO, the incoming president of Mexico who takes office December 1. The Washington Post confirmed the tentative deal in an interview with Olga Sanchez Cordero, AMLO’s incoming interior minister. A subsequent statement from Sanchez Cordero’s office said that “There is no agreement of any sort between the future government of Mexico and the one in the US,” but that’s not necessarily inconsistent with a deal currently getting worked out.
• Under the deal, asylum-seekers would have to demonstrate a reasonable fear of remaining in Mexico in order to be allowed to stay in the United States. The initial screening interview for asylum-seekers requires them to show a credible fear of persecution if they’re deported to their home countries. If they meet that standard, they’re allowed to stay in the US while their full application for asylum is pending; if they don’t (and they don’t appeal the decision), they’re deported. Under the agreement, as the Post describes it, asylum-seekers who meet the credible-fear standard would also be asked about the prospects of staying in Mexico. If they couldn’t show a reasonable fear (a higher standard than credible fear) of staying in Mexico, they’d still be allowed to apply for asylum in the US, but they’d wait in Mexico until their case was completed.
• As a result, in theory, the majority of Central Americans and other asylum-seekers who travel through Mexico would be required to stay in Mexico while their asylum cases were pending in the United States. Right now, it can take months — or years — for an asylum-seeker who’s not detained in a US immigration detention center to have her asylum case evaluated. It’s not clear whether asylum-seekers waiting in Mexico would be processed on an expedited schedule, and, if so, whether that wouldn’t further delay processing for people waiting for asylum in the US.
• Key details of the plan are still being worked out. According to the Post article, “Senior U.S. officials said they want more assurances on how Mexico intends to keep asylum seekers safe and to ensure they don’t get deported back to Central America before their asylum claims get resolved.” Those are substantial questions, not least because the US is obligated under international law not to send an asylum-seeker back to persecution — even if they themselves are not the country doing the deporting.
• Asylum officers are already being sent to San Diego to prepare for implementing the policy. An email from a senior official at US Citizenship and Immigration Services, sent out late Wednesday, asked for volunteers who might be sent to San Diego “as early as Friday,” though details were scarce. The Post believes the officers are being sent to implement the new policy, as the US will need a lot of asylum officers at ports of entry to conduct the interviews that will ensure they’re not sending anyone back to danger in Mexico.

What we don’t know about the US/Mexico asylum deal and the “Remain in Mexico” policy

• When the US will start implementing a “Remain in Mexico” policy. Lopez Obrador takes office on December 1, so it’s probable that the US-Mexico agreement will be signed no sooner than that. (And it could take several more days or even weeks to work out remaining details.) But it’s not totally clear that the US is going to wait to have a formal agreement. On Wednesday, the Post reported that Trump senior policy adviser and immigration guru Stephen Miller wanted to start implementing a “Remain in Mexico” policy immediately — even while negotiations with Mexico were ongoing. The Saturday report from the Post doesn’t clarify whether this possibility is still on the table or not.
• What legal authority the US will use to implement “Remain in Mexico.” There is a provision in US law that allows the US to force applicants for admission to remain in a “contiguous country” while their claims are being processed. But it’s not clear whether they’re using this provision for the “Remain in Mexico” plan. Because that’s ambiguous, there are lots of other unresolved questions, including…
• Whether the policy will apply to people apprehended by Border Patrol after crossing into the US, or whether it will only apply for people presenting themselves legally at official ports of entry to seek asylum. The “contiguous countries” provision applies to both cases. But the Post’s reporting implies that “Remain in Mexico” will only apply at ports. On the one hand, pushing people back to Mexico after they’ve crossed into the US could run afoul of the statutory US right to seek asylum. On the other hand, allowing people who cross into the US illegally to stay, while barring those who enter legally by presenting themselves at a port of entry, would make it even harder for the Trump administration to argue they’re trying to encourage asylum-seekers to come legally. (That’s the argument the White House is currently using to defend the asylum ban in federal court.)
• Whether the US will need to do anything beyond signing an agreement with Mexico to ratify the policy. In theory, if the policy requires the US to do things differently than the current regulations regarding asylum specify, they’ll have to rewrite those regulations (something the executive branch can do without Congress, as long as it follows proper procedures and doesn’t contradict a Congressionally-enacted law). They could propose a regulation that would take effect immediately, as they did with the asylum ban. Such a change would probably be challenged in court (as the asylum ban was) but might be on firmer legal ground than the asylum ban.
• How people will be taken care of while waiting in Mexico. Migrant shelters along the border are already overcrowded, and Tijuana is currently struggling to house 5,000 asylum-seekers (thousands of whom have arrived in the last week as part of the fall “caravan,” but others of whom have been waiting for weeks or months to be admitted at the port of entry). The Post says the US doesn’t appear to be offering any financial support to Mexico to feed, shelter and care for asylum-seekers while they wait. Some business owners in Tijuana have reportedly offered to give jobs to asylum-seekers, but it’s not clear how they’d be able to work legally in Mexico without seeking legal status there — and getting legal status in Mexico could make it much harder for them to get asylum in the US.
• How this will be challenged in court and if it will ultimately be found legal. It is inevitable that advocates will sue to block the “Remain in Mexico” policy. But because so many things about it are still unclear, it’s not clear what exactly their basis for a lawsuit will be. The “Remain in Mexico” policy is another legally aggressive step on asylum, an area of law where Congress has pretty clearly spelled out what’s supposed to happen. On the other hand, the judicial branch tends to extend the executive branch a lot of deference when foreign policy is involved. Ultimately, the prospects of the Remain in Mexico policy might not be apparent until the policy has already been put in place — and in the meantime, asylum-seekers will be the subjects of a binational experiment.