“SHALOM, MAHMOUD.” That’s how the White House announced the detention and planned deportation of Mahmoud Khalil, a recent Columbia University graduate who was an organizer of last year’s anti-Israel encampment on campus. 

President Donald Trump called Khalil, who grew up in Syria but is of Palestinian descent, “a radical foreign pro-Hamas student,” and said the former graduate student’s arrest was the “first arrest of many to come” as his administration began to target “terrorist sympathizers.” The move escalated Trump’s long-standing commitment to deport foreign students who support terrorism, which he made a priority in a January executive order on combating antisemitism. 

While Khalil, who is 30, first came to the U.S. on a student visa, he later received a green card. As a lawful permanent resident, Khalil has a stronger claim to due process protections than he would as a foreign national in the U.S. on a time-bound student visa — which has raised questions for some legal experts about the legality of Trump’s move to arrest and deport Khalil. On Monday, a federal judge in New York blocked his deportation pending further proceedings. 

“I consider myself on the right, and I wouldn’t have any objection to student visa action,” said Paul Rosenzweig, a former Republican Department of Homeland Security official and a national security lawyer. “Maybe this guy shouldn’t have gotten a green card in the first instance. But he’s got one now, and that means he has rights.” 

Central to the issue is a debate over whether Khalil’s activism — as one of the encampment’s lead negotiators and an advocate for divestment from Israel — should be considered free speech, protected by the First Amendment, or whether it should be viewed as support for terrorism. 

“There is some obvious ambiguity about what counts as expressing support for terrorism. You could define that narrowly or broadly,” said Ilya Somin, a law professor at George Mason University. “When we talk about pro-terrorist speech or other kinds of categories of objectionable speech, a lot of them have a high degree of fuzziness about their meaning.” 

A DHS spokesperson said on Sunday that Khalil “led activities aligned to Hamas, a designated terrorist organization.” The Trump administration had not yet outlined the details of their allegations, such as whether Khalil himself made any concerning comments or if he participated in unlawful activity, like the violent occupation of a campus building last April. Khalil also hadn’t been charged with a crime. Spokespeople at the State Department and DHS did not respond to requests for comment on Monday.

Federal immigration law states that a foreigner is “inadmissible” if they have endorsed or espoused “terrorist activity” or persuaded others to do so, or if they “support a terrorist organization.” They are also deemed ineligible to be in the U.S. if officials have “reasonable ground to believe” someone “is a representative of a terrorist organization or a political, social or other group that endorses or espouses terrorist activity.” But what is considered support for terrorism is a difficult legal question, particularly as it relates to immigrants and visa holders.  

“They’ll try to say, ‘Oh, this remark or that remark is espousing terrorism and encouraging other people to do so,’” said Elizabeth Keyes, a professor at the University of Baltimore School of Law. She argued that the terrorism argument may be a way for Trump to target anti-Israel speech. 

“What they’re really doing is trying to make sure people are afraid to express their political viewpoints, and that’s a First Amendment problem,” Keyes continued. “Even though this will be litigated in some way, shape or form in immigration court, there’s also going to be First Amendment challenges.” 

The key question, according to Will Creeley, a First Amendment attorney and the legal director of the Foundation for Individual Rights and Expression, is whether Khalil engaged in unlawful conduct in the course of his participation in last year’s encampment. The Trump administration has not provided answers on that front.

“The way I’ve been thinking about it today is that, just as the First Amendment protects your right to wear, for example, the KKK’s white sheets or fly the communist flag, so, too, does it protect your right to distribute pamphlets about Hamas,” Creeley told Jewish Insider. “You don’t have the right to break into a library. You don’t have the right to prevent access and egress to a campus and so forth. But without that information, we just can’t tell what’s at issue here.” 

Some have argued that simply participating in the encampment rises to the level of criminal activity. Khalil was under investigation by Columbia University for alleged misconduct last year, but he was ultimately cleared and allowed to graduate in December.

“This was not mere protest activity, but involved some degree of criminality,” said Ken Marcus, founder and chairman of the Louis D. Brandeis Center for Human Rights Under Law, which litigates civil rights cases alleging antisemitism at U.S. universities. “The federal government is not prosecuting people for engaging in political speech. The federal government is addressing criminality, violation of school rules and violation of the terms of either green cards or student visas.” 

Revoking student visas is a much less onerous process than doing so for a green card. Revocation of a green card requires the holder to appear before an immigration judge — unlike the arrest and deportation of undocumented immigrants, another priority of the Trump administration, which has dispatched Immigrations and Customs Enforcement agents to major cities to deport immigrants who lack legal status. 

“Sometimes courts are reluctant to infringe upon the liberties of green card holders in a way that they’re not reluctant if it’s somebody who’s here temporarily or somebody who’s here without status at all,” said Keyes. That is not to say that a person with a green card must be convicted of, or even charged with, a crime to have their legal status revoked. 

“Many of the grounds don’t require convictions. It’s just the administration saying this person is trying to get other people to support a terrorist organization, and they have enormous latitude to determine who’s a terrorist organization,” added Keyes. 

A petition filed by Khalil’s lawyer alleges that the four DHS agents who arrested him at his home on Saturday night told him they were there to revoke his student visa, suggesting they were not aware that he now holds a green card. When he showed them documents proving he has a green card, they said they were revoking that, too. 

“It’s much easier to revoke those visas than to revoke green cards. And it may be that they initially thought that he only had a student visa, when, in reality, he had a green card,” said Somin. “Green cards can only be revoked for a relatively narrow set of specified reasons. Whether providing support to terrorism or expressing such support can qualify as such a reason is a question that perhaps will now be litigated.”