Mahmoud Khalil, a lawful U.S. resident who was a graduate student at Columbia until December, was detained Saturday by federal immigration agents in New York and flown to an immigration jail in Louisiana.

“We know there are more students at Columbia and other Universities across the Country who have engaged in pro-terrorist, anti-Semitic, anti-American activity,” Trump wrote in a social media post. “We will find, apprehend, and deport these terrorist sympathizers from our country — never to return again.”

But a federal judge in New York City ordered Monday that Khalil not be deported while the court considered a legal challenge brought by his lawyers. A hearing is scheduled for Wednesday.

Khalil’s detention drew outrage from civil rights groups and free speech advocates, who accused the administration of using its immigration enforcement powers to squelch criticism of Israel.

He is the first person known to be detained for deportation under Trump’s promised crackdown on student protests.

Federal immigration authorities also visited a second international student at Columbia on Friday evening and attempted to take her into custody but were not allowed to enter the apartment, according to a union representing the student.

Khalil, 30, had not been charged with any crime related to his activism, but Trump has argued that protesters forfeited their rights to remain in the country by protests he claimed support Hamas, the Palestinian group that attacked Israel on Oct. 7, 2023. The U.S. has designated Hamas as a terrorist organization.

Khalil and other student leaders of Columbia University Apartheid Divest have rejected claims of antisemitism, saying they are part of a broader anti-war movement that also includes Jewish students and groups. But the protest coalition, at times, has also voiced support for leaders of Hamas and Hezbollah, another Islamist organization designated by the U.S. as a terrorist group.

The U.S. Education Department on Monday warned some 60 colleges, including Harvard and Cornell, that they could lose federal money if they fail to uphold civil rights laws against antisemitism and ensure “uninterrupted access” to campus facilities and education opportunities. The Trump administration is already pulling $400 million from Columbia.

A group of Columbia faculty members expressed concern Monday that Khalil’s detention was intended to suppress free speech by students and staff who are not U.S. citizens.

“The attack on Mahmoud Khalil is intended to make them quake in their boots, and to make all of us quake in our boots,” said Michael Thaddeus, a Columbia math professor. “Our message to Washington is that we are not silenced, we are not afraid, and we stand together, determined to defeat this ongoing assault on our fundamental rights.”

In their legal complaint, Khalil’s attorneys accused the government of retaliating against him for his “constitutionally protected advocacy on behalf of Palestinian human rights.”

Typically, the government has to meet a higher bar to expel a person who has permanent residency in the U.S., like showing someone has been convicted of a serious crime.

Born in Syria to Palestinian parents, Khalil entered the U.S. to attend Columbia in 2022. He subsequently got married to an American citizen, who is now eight months pregnant.

Khalil emerged as one of the most visible activists in large protests at Columbia last year, serving as a mediator on behalf of pro-Palestinian activists and Muslim students. That role put him in direct touch with university leaders and the press — and drew attention from pro-Israel activists, who in recent weeks called on the Trump administration to deport him.

“He took a public facing role, and now he’s being targeted for speaking to the media,” another student protester, Maryam Alwan, told The Associated Press.

More recently, Khalil faced investigation by a new disciplinary body set up at Columbia University, which sent him a letter last month accusing him of potentially violating a new harassment policy by calling a school official a “genocidal dean” online.

Khalil told The Associated Press last week that he served as a spokesperson for protesters but did not play a leadership role.

“They are alleging that I was the leader of CUAD or the social media person, which is very far from reality,” he said, using the acronym for Columbia University Apartheid Divest.

Khalil received a master’s degree from Columbia’s School of International and Public Affairs last semester. He previously graduated from the Lebanese American University in Beirut with a computer science degree and worked at the British Embassy in Beirut’s Syria office, according to his biography on the Society for International Development’s website.

A few hundred protesters rallied near an Immigration and Customs Enforcement field office in Manhattan on Monday to demand Khalil’s release.

“By arresting Mahmoud, Trump thinks he can strip us of our rights and strip us of our commitment to our people,” Ibtihal Malley, a New York University student, told the crowd. “To that we say: You are wrong.”

Back on campus, Columbia sophomore Pearson Lund was among those who found the potential stripping of Khalil’s green card concerning.

“At what point does this process stop?” the physics student said as he entered campus through a security line guarded by city police officers.