Washington, United States — A US federal judge has ordered the Trump administration to "facilitate" the return to the United States of a Salvadoran migrant wrongly deported to his home country, and directed it to report Friday on those steps. 

Judge Paula Xinis is to preside over a hearing, the latest in a high-stakes legal wrangle over the executive branch's powers to expel undocumented migrants, early Friday afternoon.

Kilmar Abrego Garcia, a Salvadoran living in the eastern state of Maryland and married to a US citizen, was arrested 12 March by immigration police.

He was among more than 200 people deported on 15 March to a notorious prison in El Salvador, as part of Donald Trump's migration crackdown. 

Most of those expelled were accused by the administration of belonging to a Venezuelan gang, Tren de Aragua, which Washington has labeled a terrorist organization.

As Abrego Garcia's family proclaimed his innocence, an administration lawyer acknowledged that his expulsion followed an "administrative error," since a federal court in 2019 ruled he could not be expelled to El Salvador, where his life could be in danger.

The case represents the only time the administration has acknowledged wrongly deporting anyone. 

The administration, however, said it was powerless to secure Abrego Garcia's return from the high-security Salvadoran prison and insisted he was part of MS-13, a Salvadoran gang the United States classified as terrorist in February.

Xinis initially rejected the administration arguments, saying it had shown no proof that Abrego Garcia was a gang member, and demanding that the government "facilitate" his return to the US by 7 April at the latest.

A federal appeals court rejected the administration's appeal.

The conservative-dominated Supreme Court on Monday issued a stay of the district judge's repatriation order pending further consideration.

The high court also held that the administration was indeed required to "facilitate" Garcia's return and to ensure that he be treated as if he had never been wrongly deported. 

But the justices also directed Xinis to clarify her order for the government to "effectuate" Abrego Garcia's release -- saying she may have exceeded her authority and needed to reflect "due regard for the deference owed to the Executive Branch in the conduct of foreign affairs."

She subsequently amended her wording to say the government must take "all available steps to facilitate" his return "as soon as possible," not setting any deadline.

The administration has described the case as a key test of the president's power to conduct sensitive national security-related operations.

Xinis also directed the administration to provide an update on Abrego Garcia's current location, and to explain the legal grounds on which he was detained.

The hearing Friday, at the federal courthouse in Greenbelt, Maryland, is scheduled for 1:00 pm (1700 GMT).