After Judge James Boasberg temporarily blocked the use of the 18th-century wartime law as a legal justification for deportations in March, he will hear arguments on Thursday for and against the expulsions.

This block is in place through April 12. This week, the U.S. sent 17 more migrants to a prison in El Salvador, but it's unclear what legal grounds were used. Boasberg has asked the Trump legal team to return to court to explain itself.

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Boasberg is among several district judges deciding whether to lift a March 15 order temporarily prohibiting deportations under the Alien Enemies Act of 1798. Boasberg was critical of the Trump administration's usage of the act when issuing a temporary restraining order last month.

The administration has transferred hundreds of immigrants to El Salvador, invoking the Alien Enemies Act for the first time since World War II.

The Alien Enemies Act allows noncitizens to be deported without the opportunity to go before an immigration or federal court judge. President Donald Trump issued a proclamation calling the Tren de Aragua gang an invading force. Boasberg, an Obama nominee, had previously ruled that immigrants facing deportation must get an opportunity to challenge their designations as alleged gang members. He said there is “a strong public interest in preventing the mistaken deportation of people based on categories they have no right to challenge.”

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Boasberg's ruling seemed to portend an admitted error by the Trump administration. Earlier this week, the Trump administration admitted it erred in deporting a migrant to El Salvador on March 15 who was given asylum in 2019. Kilmer Armado Abrego-Garcia was deported on March 15 as the U.S. sent three planes from the U.S. to El Salvador, purporting that those on the planes were members of the Tren de Aragua and MS-13 gangs.

Abrego-Garcia had been accused of being a member of the MS-13 gang, but prosecutors could not prove it. The Trump administration said it would not make any effort to return Abrego-Garcia to the U.S.