The Supreme Court on Thursday ordered the Trump administration to try to return a wrongly deported immigrant from a high-security prison in El Salvador where he is being held.

The unsigned, unanimous ruling said the Trump administration should try to have Maryland resident Kilmar Armando Abrego Garcia returned from the Salvadorian prison known as CECOT so that he can have immigration proceedings.

The Trump administration deported Abrego Garcia last month in what it acknowledged was an “administrative error” despite a court order that he not be sent to El Salvador.

The Supreme Court decision Thursday upheld a lower-court order for Abrego Garcia to be brought back to the United States.

“The order properly requires the Government to ‘facilitate’ Abrego Garcia’s release from custody in El Salvador and to ensure that his case is handled as it would have been had he not been improperly sent to El Salvador,” the decision said.

After Abrego Garcia’s family sued the Trump administration, Judge Paula Xinis for the U.S. District Court for the District of Maryland ordered the Trump administration to return Abrego Garcia to the United States by Monday evening.

Then on Monday, a unanimous three-judge decision from the U.S. Court of Appeals for the 4th Circuit upheld that judge’s order to return Garcia to the United States. The Trump administration asked the justices to intervene and they granted a temporary stay before issuing Thursday’s order.

Trump officials argued that Xinis had overstepped her bounds and sought to mandate U.S. foreign policy.

The unsigned order said that Xinis’ decision was proper, but that Xinis should clarify it “with due regard for the deference owed to the Executive Branch in the conduct of foreign affairs.”

Justices Sonia Sotomayor, Elena Kagan and Ketanji Brown Jackson wrote separately to emphasize the “egregious” error of the government and criticize the argument the Trump administration made to avoid returning Abrego Garcia.

“The Government’s argument, moreover, implies that it could deport and incarcerate any person, including U.S. citizens, without legal consequence, so long as it does so before a court can intervene,” the justices wrote. “That view refutes itself.”

Abrego Garcia’s case has gained prominence in reaction to Trump’s broad assertion of deportation powers, as Democratic members of Congress have demanded his return.

On Thursday members of the Maryland congressional delegation held a rally with Abrego Garcia’s family. The Congressional Hispanic Caucus also sent a letter to the Trump administration about Abrego Garcia’s deportation.

The Trump administration has alleged that Abrego Garcia, who has not been charged with a crime, was a member of MS-13 and eligible for deportation. Thursday’s Supreme Court decision noted that he has denied being a member of the gang.

The case is Kristi Noem et al. v Kilmar Armando Abrego Garcia et al.