President Donald Trump can’t get his border wall built, but he's been creating policies so that he doesn't need to, building an invisible wall to foreclose upon the possibility of migration from Central America. His attacks on asylum-seekers — primarily migrants from El Salvador, Guatemala and Honduras who are fleeing violence, rape, persecution and social breakdown in their home countries — have proven more successful than any physical barrier in restricting their access to humanitarian protection.

The Supreme Court validated his latest blow to the system on Wednesday by allowing his latest “asylum ban” to proceed even as various legal challenges are still pending in the lower courts. The ban effectively bars asylum seekers from filing their claim in the U.S. by directing them to seek asylum first in any so-called safe third country through which they traveled en route to the U.S. Never mind that no such country exists; Trump insists the refugees belong anywhere but on American soil.

Over the past year, the administration has systematically attacked the rights of asylum-seekers by incarcerating them, restricting their access to the courts and keeping them out of the country altogether.

In the courts, the Justice Department has sought to narrow the legal scope for seeking humanitarian relief by pre-empting claims based on gang violence, intimate partner abuse or family membership. At the border, the Trump administration tried to block asylum-seekers from entering unless they presented themselves at a designated port of entry. Then it tried to keep them away from the border altogether by imposing the “remain in Mexico” policy, which effectively forced migrants to wait indefinitely on the Mexican side while pursuing their asylum claims. Asylum-seekers have in turn been trapped in a chaotic environment at the border, exposed to economic exploitation, housing instability and violence, which will likely deepen the scars of the social trauma they suffered on their journey — including sexual assault and human trafficking.

Migrants stuck in Mexico also typically lack access to any form of legal help, which is critical for navigating the court system, especially when one is trying to litigate a claim in a U.S. courtroom while, say, living in a shelter in Juarez. As of late June, according to the Transactional Records Access Clearinghouse, out of nearly 13,000 migrants with pending cases who had been forced to wait in Mexico, just 163, or 1.3 percent, had managed to obtain a lawyer.

The criminalization of border-crossers has led to systematic family separation, despite the administration’s claims of having ended the practice. In one case detailed by the Women’s Refugee Commission, border patrol officials separated Alvaro, an indigenous Guatemalan father, from his son at the border, and sent Alvaro to Mexico while his son remain in the U.S. It was only with the help of pro-bono lawyers that he was allowed back into the U.S. to reunite with his child, three months later. Countless other families may now have to sacrifice unity for survival, splitting up in order for one part of the family to claim asylum while others go back across the Mexican border or return home.

Trump spins this cruelty into a campaign talking point: At a rally in March he mocked Central American migrants' asylum claims as “a big, fat con job.”

While the "remain in Mexico" policy is suspending migrants in legal purgatory, the Trump administration has sought to designate Guatemala as a “safe third country” where migrants from other parts of Central America might apply for asylum. The move, which has been roundly condemned in both the U.S. and Guatemala, ignores the fact that Guatemala’s human rights situation is so dire that it is contributing to the migration flow from Central America, not hosting refugees from elsewhere.

For asylum-seekers who have managed to remain in the U.S. despite the policies, the administration is determined to make life as miserable as possible: It has moved to rollback long-standing protections for children and allow indefinite detention of whole families; immigration authorities have issued a directive to tighten the legal process for “unaccompanied” migrant children — who arrive at the border without a caregiver — which could needlessly undermine due process for some of the most vulnerable migrant youth. Trump has also proposed charging a fee to asylum-seekers while at the same time banning them from working while their cases are pending — apparently with the aim of impoverishing them as much as possible while they pursue their claims in court.

In the background, the conditions at immigrant detention centers continue to deteriorate, and Trump has slashed foreign aid to El Salvador, Guatemala and Honduras — delivering a double blow of collective punishment across the region.

So far, many of Trump's most extreme anti-immigrant policies have been blocked through court challenges, including Trump’s latest asylum ban. But after various district and appeals court rulings resulted in a split injunction — blocking the ban in some states but not others — the Supreme Court gave a green light to let the administration impose the ban nationwide, forcing asylum-seekers to seek refuge in a nonexistent “safe” transit country.

Arguably, not even the U.S. can be considered a safe country for asylum-seekers. But there is a robust grassroots resistance at work here, with advocacy groups providing legal aid to asylum-seekers across borders, helping separated families reunite and delivering basic social services. However, every day that Trump’s asylum ban is imposed is another day of flouting the government’s responsibility under international humanitarian law, and another day of ignoring the historical debt that Washington owes to Central America after decades of destabilizing and intervening in the region.

Although Trump’s plans to build his fantastical border wall may have stalled, he is constructing a more insidious barrier through the law, by reshaping the framework of humanitarian policy into a cudgel for imprisoning, abusing and exiling people who have already seen the worst of humanity. A physical wall, at least, could be quickly knocked down under a new president. The legal fortress Trump has embedded at the border and in the courts could take generations to dismantle.