Washington DC – The Supreme Court ruled 6-3 on Tuesday that the controversial Remain in Mexico policy, halted by the Biden Administration, must be reinstated.

All six conservative justices ruled against blocking a lower court order to reinstate the Trump-era Migrant Protection Protocols (MPP), also known as Remain in Mexico, the Associated Press reported.

During the Trump administration, tens of thousands of asylum seekers were sent to Mexico between 2019 and 2021, often waiting years in dangerous locations for US court dates.

In June, Homeland Security Secretary Alejandro Mayorkas issued a memo announcing the end of the program, but a Trump-appointed US district judge in Texas earlier this August ruled that the MPP must be reinstated.

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The American Civil Liberties Union (ACLU) is now urging the Biden administration to develop more robust reasoning for ending the program that will stand up better against court challenges.

"The government must take all steps available to fully end this illegal program, including by re-terminating it with a fuller explanation. What it must not do is use this decision as cover for abandoning its commitment to restore a fair asylum system," said Omar Jadwat of the ACLU's immigrant rights project.

Whether the administration will do so is unclear, as Vice reported earlier this month that senior White House officials had privately met to discuss reinstating the MPP, to the alarm of immigrant rights advocates.

Since Biden suspended the MPP upon taking office, most migrants have been turned back at the Southern border on another Trump-era policy – a public health order dating to the start of the pandemic.