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 Sunday.

The arrest of the activist, a legal permanent resident of the United States, was a significant escalation of President Donald 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.

The arrest, she said, “follows the U.S. government’s open repression of student activism and political speech.”

Greer said she was not sure of Khalil’s “precise whereabouts,” and that he may have been transferred as far away as Louisiana.

U.S. Immigration and Customs Enforcement and the Department of Homeland Security did not immediately reply to a request for comment. On Sunday, Secretary of State Marco Rubio shared a link on social platform X to a news article about Khalil’s arrest and issued a broad promise: “We will be revoking the visas and/or green cards of Hamas supporters in America so they can be deported.”

The immigration agents who detained Khalil told him his student visa had been revoked, Greer said, even though he does not currently hold such a visa. Revoking a green card is quite rare, said Elora Mukherjee, director of the immigrants’ rights clinic at Columbia Law School, and in a vast majority of cases where it does happen, the holder has been accused and convicted of criminal offenses, she said.

Khalil was a fixture at the protests that engulfed Columbia last spring, making the New York City campus the national epicenter of demonstrations against the war in the Gaza Strip. He described his role to reporters as a negotiator and spokesperson for Columbia’s pro-Palestinian group, Columbia University Apartheid Divest.

In a statement Sunday, Columbia administrators did not comment directly on the arrest.

“Columbia is committed to complying with all legal obligations and supporting our student body and campus community,” the statement read. “We are also committed to the legal rights of our students and urge all members of the community to be respectful of those rights.”

This article originally appeared in The New York Times.

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