Federal immigration authorities on Saturday detained a well-known activist who played a major role in Columbia University’s pro-Palestinian student movement last year, his lawyer said on Sunday.

The arrest of the activist, a legal permanent resident of the United States, was a significant escalation of President Trump’s crackdown on what he has called antisemitic campus activity.

The activist, Mahmoud Khalil, is of Palestinian heritage and graduated in December with a master’s degree from the university’s school of international affairs, according to his LinkedIn. His lawyer, Amy Greer, confirmed that he was a green card holder and said the arrest would face a vigorous legal challenge.

“We will vigorously be pursuing Mahmoud’s rights in court, and will continue our efforts to right this terrible and inexcusable — and calculated — wrong committed against him,” Ms. Greer said in a statement. The arrest, she said, “follows the U.S. government’s open repression of student activism and political speech.”

Ms. Greer said she was not sure of Mr. Khalil’s “precise whereabouts,” and that he may have been transferred as far away as Louisiana. Mr. Khalil’s wife, an American citizen who is eight months pregnant, tried to visit him at a detention center in New Jersey but was told he was not being held there, Ms. Greer said.

A spokeswoman for the Department of Homeland Security, Tricia McLaughlin, said in a statement on Sunday night that Mr. Khalil had been arrested “in support of President Trump’s executive orders prohibiting antisemitism.”

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