Mahmoud Khalil, a recent graduate student at Columbia University and green-card holder, was arrested by Immigration and Customs Enforcement officers over the weekend in what is likely one of the first high-profile detentions of a student who participated in the protests against the Israel-Hamas war.

The arrest follows through on one of President Trump’s executive actions, which directed the government to use all of its tools to punish those who have engaged in “antisemitic harassment and violence.” The executive action cites the federal law that authorizes deporting a foreign national who “endorses or espouses terrorist activity.”

In a social media post on Monday, Trump said the arrest was the first of many to come. He vowed that his administration “will find, apprehend, and deport these terrorist sympathizers from our country — never to return again.”

People dance and wave large Israeli flags during a rally against campus antisemitism at George Washington University in May 2024 in Washington, D.C.

Michael Thaddeus, a mathematics professor at Columbia University, said the move seeking to strip Khalil’s green card and deport him violates the broader trust from foreign students who come to study in the U.S.

“They come because of their trust and belief that they could speak out freely while they’re here and not be imprisoned or harassed because [of] their political speech or activism or advocacy,” Thaddeus said.

First, they told Khalil, who’s of Palestinian descent, that his student visa had been canceled. But he’s not on a visa; he’s a legal permanent resident. His wife went to get his green card from their apartment, but officers said his lawful permanent residency had been revoked.

During Trump’s first term, he took steps towards limiting visas for foreign nationals and revoking people’s immigration status, including denaturalization, or cancelling someone’s status as a naturalized U.S. citizen.