A Palestinian protest leader at Columbia University was arrested by Department of Homeland Security agents Saturday night despite having a green card, his attorney said.

President Donald Trump has promised to deport international students who participated in “pro-jihadist protests” on college campuses. Columbia was at the center of intense protests that broke out on campuses across the country last year over the Israel-Gaza war. The arrest came just one day after the Trump administration said it was canceling $400 million in federal contracts and grants to Columbia because university officials had not done enough to prevent antisemitism on campus.

Mahmoud Khalil, who as a Palestinian graduate student was a leader in negotiations between protesters and Columbia officials last spring, was stopped by U.S. Immigration and Customs Enforcement agents who told him his student visa had been revoked, his attorney Amy E. Greer said in a written statement. When Khalil told agents that he was a lawful permanent resident, holding a green card, agents detained him anyway, she said.

Greer said she filed a habeas corpus petition on Khalil’s behalf challenging the validity of his arrest and detention. An ICE detainee locator website says Khalil is being held in Elizabeth, New Jersey. Greer was told Sunday morning he was there. But Greer said Khalil’s wife, who is eight months pregnant, a U.S. citizen and had also been threatened with arrest, tried to visit him there Sunday and was told he was not there.

“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,” Greer said. She said the arrest “follows the U.S. government’s open repression of student activism and political speech, specifically targeting students at Columbia University for criticism of Israel’s assault on Gaza. The U.S. government has made clear that they will use immigration enforcement as a tool to suppress that speech.”

She said many people and organizations have expressed support for Khalil and that he appreciates that.

A spokesman for ICE referred questions to the State Department. A State Department spokesperson said Sunday, “Visa records are confidential under U.S. law. Therefore, we cannot comment on individual visa cases.” The spokesperson referred questions back to ICE for answers about Khalil’s detention.

Protests over the war have prompted national debate over the First Amendment and student safety, with some arguing that curbing demonstrations violates participants’ rights to free speech and assembly, and others contending that some of the language and symbols used by some protesters is offensive and threatening to Jewish people.

Columbia’s interim president, Katrina Armstrong, said Friday that taking serious action against antisemitism on campus was the school’s No. 1 priority.

Trump has said his administration would revoke student visas of Hamas sympathizers, and he warned “resident aliens who joined in the pro-jihadist protests” on college campuses, “we will find you, and we will deport you.” He has also said that foreign “agitators will be imprisoned/or permanently sent back to the country from which they came.”

International students can lose their visas if they are convicted of a crime or if they don’t take the required number of courses because they have been suspended, according to the Immigration and Nationality Act. They can’t have their visas revoked for beliefs or statements that are within the bounds of the law. But foreign nationals who endorse or are associated with terrorist groups could lose their visas.

In January, Khalil, who had been a vocal activist at Columbia, had responded to Trump’s threat by saying it was racist to label pro-Palestinian protesters as terrorists. He also said it would undermine fundamental rights to free speech and assembly and set a dangerous precedent in which peaceful protest is punished with severe consequences.

The public statements by some protesters at Columbia hardened in tenor this year, even as the scope and scale of demonstrations has been much smaller. Columbia University Apartheid Divest, which Khalil had sometimes spoken for in response to questions from reporters, has in the past praised the leadership of Hamas, Hezbollah and Ansarallah, which are all U.S.-designated terrorist organizations.

Some Jewish students and organizations have welcomed the Trump administration’s actions at Columbia.

Activists launched a petition demanding Khalil’s release that already has generated more than 300,000 signatures or notes of support, according to a website for the drive.

On Sunday, the union Student Workers of Columbia called on the university’s leaders to be a sanctuary campus and protect its students and employees.

In a statement, Columbia University said, “There have been reports of ICE around campus,” and that the school has and will continue to follow the law. “Consistent with our long-standing practice and the practice of cities and institutions throughout the country, law enforcement must have a judicial warrant to enter nonpublic University areas, including University buildings. Columbia is committed to complying with all legal obligations and supporting our student body and campus community.”

The university’s protocol states that in general ICE agents must have a judicial warrant or subpoena to access nonpublic areas such as classrooms and housing, but that “exigent circumstances may allow for access to University buildings or people without a warrant.”