U.S. President Joe Biden received a major setback to his governing goals a few days ago: he must reinstate the controversial Donald Trump-era immigration policy known as the "Remain in Mexico" program. On Tuesday, the U.S. Supreme Court rejected the Biden administration's request to stay a lower court order requiring the revival of Trump's policy, officially known as the Migrant Protection Protocols (MPP).

Three liberal justices on the Court publicly indicated that they would have granted the request to stop the lower court's order; however, it was not enough to completely halt the order. Therefore, the "Remain in Mexico" program must be reinstated. Before reaching this point, several things happened with the MPP policy. Here are the most important points.

What is "Remain in Mexico"?

This Trump-era policy was officially unveiled on Thursday, December 20, 2018. On that day, Kirstjen Nielsen, who at the time was secretary of the Department of Homeland Security (DHS), announced that the United States had informed Mexico that people who entered the country illegally or who entered without proper documentation and requested asylum would be sent to Mexico to await the resolution of their immigration proceedings in the US. Asylum seekers from Guatemala, Honduras, and El Salvador were to wait outside the U.S. until their immigration proceedings were concluded, according to DHS.

More details of Trump's policy

In a nutshell, this policy forced migrants to remain in Mexico until their U.S. immigration court hearing date. According to DHS, the migrants would first be returned to Mexico, then notified to appear in court, and then allowed to enter the country to attend the hearing. A DHS official stated at the time that Mexico would continue to provide humanitarian assistance to individuals awaiting legal proceedings near the border.

What happened to the "Remain in Mexico" program with Biden's arrival?

This policy faced several processes to have it reversed in the Trump administration. However, nothing could be done about it... until Biden became president. Shortly after President Joe Biden took office on January 20, 2021, DHS suspended new enrollments to the MPP program. Subsequently, Biden's DHS began the process of gradually allowing asylum-seekers previously subject to the "Remain in Mexico" program into the United States.

And it was on Thursday, June 1, that Alejandro Mayorkas, DHS secretary, announced that the Biden administration was formally ending the Trump-era policy. "I am directing DHS staff to take all appropriate actions to terminate the MPP, including taking all necessary steps to rescind the implementing guidance and other directives or policy guidance issued to implement the program," Mayorkas wrote in a memo.

The most recent blip: Trump-era policy is back

In April, a few months before the formal termination of the program, Texas, and Missouri sued the U.S. government to reinstate a program that had already been suspended since Biden's start in the office. This month, already with the formal end of the MPP policy, U.S. District Judge Matthew Kacsmaryk, a Trump appointee, said the Biden administration violated the Administrative Procedure Act (which requires government agencies to follow certain procedural steps when implementing policies) in the way it got rid of the "Remain in Mexico" program, so it had to restore it.

Then, the Biden administration appealed to the Supreme Court on Friday, August 20 after the U.S. Fifth Circuit Court of Appeals said a day earlier that it would not stay U.S. District Judge Kacsmaryk's order to revive the program. This brings us to Tuesday's August 24 decision by the U.S. Supreme Court, in which it rejected the Biden administration's request. At this point, it goes so far.