HYATTSVILLE, Md. — A federal judge Friday ordered the Trump administration to arrange for the return of a Maryland man to the United States after he was mistakenly deported to a notorious El Salvador prison, while a U.S. government attorney was at a loss to explain what happened.

U.S. Immigration and Customs Enforcement expelled Kilmar Abrego Garcia last month despite an immigration judge’s 2019 ruling that shielded him from deportation to his native El Salvador, where he faced likely persecution by local gangs.

Before she issued her ruling, U.S. District Judge Paula Xinis described Abrego Garcia’s deportation as “an illegal act” and pressed a Justice Department attorney for answers, leading to a tense exchange.

Justice Department attorney Erez Reuveni conceded to Xinis that Abrego Garcia should not have been removed from the U.S. and shouldn’t have been sent to El Salvador. He couldn’t tell her what authority he was arrested under in Maryland.

The judge’s ruling came after Abrego Garcia’s wife joined supporters at a rally to urge her husband’s return.

Jennifer Vasquez Sura, a U.S. citizen, hasn’t spoken to Abrego Garcia since he was flown to his native El Salvador in March and jailed. She urged supporters to keep fighting for her husband “and all the Kilmars out there whose stories are still waiting to be heard.”

The White House has cast Kilmar Abrego Garcia, 29, as an MS-13 gang member and assert that U.S. courts lack jurisdiction over the matter because the Salvadoran national is no longer in the United States. Abrego Garcia’s attorneys have countered that there is no evidence he was in MS-13. The allegation is based on aninformant’s claim in 2019 that Abrego Garcia was a member of a chapter in New York, where he has never lived.

Abrego Garcia’s deportation, described by the White House as an “administrative error,” has outraged many and raised concerns about expelling noncitizens who were granted permission to be in the United States.

Abrego Garcia had a permit from the Department of Homeland Security to legally work in the U.S., his attorney Simon Sandoval-Moshenberg said. He served as a sheet metal apprentice and was pursuing a journeyman license.

He fled El Salvador around 2011 because he and his family were facing threats by gangs. He later married Vasquez Sura. The couple are parents to their son and her two children from a previous relationship.