The decisions suggest that the battle over using a wartime law, the Alien Enemies Act, to deport migrants is certain to persist.

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A case involving a Venezuelan migrant, Daniel Zacarias Matos, could explore the question of whether President Trump has used the Alien Enemies Act in a lawful manner.

© Tierney L. Cross for The New York Times

A case involving a Venezuelan migrant, Daniel Zacarias Matos, could explore the question of whether President Trump has used the Alien Enemies Act in a lawful manner.

© Tierney L. Cross for The New York Times

To President Trump, Judge James E. Boasberg is “a troublemaker” and a “Radical Left Lunatic.” But his record and biography, including a friendship with Justice Brett M. Kavanaugh, say otherwise.

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