U.S. Border Patrol officers return a group of migrants back to the Mexico side of the border as Mexican immigration officials check the list, in Nuevo Laredo, Mexico. (Salvador Gonzalez/AP)

WHEN THE Trump administration this year began forcing Central American asylum seekers to remain in Mexico while awaiting their day in U.S. immigration courts, the new policy was given a bloodless bureaucratic name: Migrant Protection Protocols. Now it is apparent that the “protection” granted those migrants is scant indeed. Thousands of them have been preyed on by criminal gangs, crammed into festering detention centers that are breeding grounds for disease and hamstrung by daunting impediments to finding lawyers to represent them. Dozens have been kidnapped.

The policy has subjected asylum seekers, including those with legitimate claims for humanitarian protection in the United States, to appalling risks and inhumane conditions. The Trump administration could have focused on creating an efficient system that might dissuade migrants from making the northward trek, by quickly adjudicating their applications and deporting those whose applications are denied. Instead, Washington opted for a de facto regime of deterrence outsourced to Mexico, where migrants are neglected, ill-treated and victimized.

The Post’s Kevin Sieff described cases in which Central American migrants, returned to Mexico by U.S. authorities, have been seized by kidnappers who demanded ransom from their relatives at home and in the United States. That’s chilling; it’s also unsurprising and predictable in Mexican border areas such as Tamaulipas, to which migrants are being returned, which the State Department acknowledges is dangerous territory.

The system grew out of President Trump’s alarm at the swelling tide of asylum seekers, mainly Central American families, who threatened to overwhelm U.S. border patrol and agencies starting last year. Beginning in January, and then in greater numbers since, asylum applicants have been sent back to Mexican border towns to await hearings. Thousands are now stuck there; some are reported to have given up.

Logistical obstacles prevent some from being notified of upcoming hearing dates. Many report problems enlisting U.S.-based lawyers to represent them in U.S. immigration court — and without one, their chances of success are all but nil.

In June, Mr. Trump strong-armed Mexican officials into agreeing to deploy thousands of national guard forces to detain and deport Central American and other migrants heading toward the United States. Many wound up in Mexican detention centers, where they are subjected to atrocious conditions. As the New York Times reported, many of the approximately 60 detention centers where migrants are held are ill-equipped for the numbers of detainees who have arrived. Basic hygiene, including showers and functioning toilets, is in short supply; so is medical attention. President Andrés Manuel López Obrador, whose administration has been criticized for its handling of the crisis by his government’s own human rights ombudsman, is pledging improvements.

The Trump administration is within its rights to seek means to deter migrants whose chances of receiving asylum are poor. But by shunting migrants to Mexico, where they face menace , inhumane living conditions and obstacles to seeking a fair adjudication of their asylum claims, the administration is complicit in a massive injustice.