Civil liberties organisations and academics have raised alarm at the detention of Mahmoud Khalil, a Palestinian student activist at Columbia University, calling it a serious breach of free-speech rights under the administration of President Donald Trump.

"Ostensibly, the moral justification is to combat anti-Semitism, always a noble goal," Nader Hashemi, a professor of Middle East and Islamic politics at Georgetown University, told Al Jazeera.

But, Hashemi warned, this justification is being used as a smoke screen to tamp down on pro-Palestinian views in the United States.

"Objectively, what is really happening is an effort to silence all public expression of support for Palestinian human rights to placate right-wing supporters of Israel within the Republican Party," he said. "That is how this topic should be framed and understood."

Agents from Immigration and Customs Enforcement (ICE) arrested Khalil on Saturday evening at his university housing, after he and his pregnant wife, an American citizen, returned from an iftar dinner.

His lawyer Amy Greer said he is a lawful permanent resident of the US. Experts have underscored that it is rare for green card holders to be threatened with deportation, except in cases of serious crimes.

Khalil, however, was a prominent figure in protests against Israel’s war in Gaza at the Ivy League university, and Trump has repeatedly voiced his desire to expel such protesters from the country.

"Many are not students, they are paid agitators," Trump wrote in a social media post on Monday, without offering evidence. He also accused student protesters of participating in "pro-terrorist, anti-Semitic, anti-American activity" — again, without proof.

Still, he warned Khalil’s detention would be "the first of many to come".

"We will find, apprehend, and deport these terrorist sympathizers from our country — never to return again."

Free speech groups point out that the Department of Homeland Security (DHS) accused Khalil of leading "activities aligned with Hamas, a designated terrorist organization".

But analysts note that the department’s allegation falls short of more tangible claims. US law, for instance, prohibits anyone in the country’s jurisdiction from providing "material support" to terrorist organisations.

The rationale provided for Khalil’s arrest, experts argue, was overly broad and could be wielded against any voices critical of Israel and US foreign policy.

"It’s a loophole so big that you could drive a truck through it," Will Creeley, the legal director of the Foundation for Individual Rights and Expression (FIRE), a free speech group, told Al Jazeera.

"I think what’s perhaps most dangerous about this moment is that, given the rhetoric coming out of the administration today, folks across the country are going to think twice before they criticise the government, whether it’s the US government or Israeli government, and that chill is a real problem," he added.

The effort to connect criticism of Israel with support for terrorism also appears to mirror Project 2025, a controversial series of policy proposals for Trump's second term compiled by the Heritage Foundation, a right-wing think tank.

The document drew alarm for its expansive interpretations of executive power, as well as its views on issues like the pro-Palestinian protest movement.

One Project 2025 proposal states that pro-Palestine protests are part of a "highly organized, global Hamas Support Network (HSN) and therefore effectively a terrorist support network".

Greer has told media outlets that, when she spoke with ICE agents over the phone, they appeared to have incorrect information about Khalil’s immigration status, informing her they were going to revoke his student visa.

Khalil, a graduate student at Columbia until December, was previously in the US on a student visa but has since obtained a green card, making him a lawful permanent resident of the country.

Greer said that, when she informed ICE agents that he was a permanent resident, they said his green card would be revoked instead.

Student negotiator Mahmoud Khalil speaks to media on the Columbia University campus on April 29, 2024 [Ted Shaffrey/AP Photo]

Nithya Nathan-Pineau, a policy lawyer with the Immigrant Legal Resource Center, told Al Jazeera that green card status can be revoked under some circumstances, such as the discovery of fraudulent information in an immigration application or certain criminal activity.

"I haven’t seen any information about criminal convictions or arrests," she said.

"It sounds like the ICE agents just unilaterally decided that whatever immigration status he had, it didn’t matter."

Greer said that she and Khalil’s wife were told he was being held in an immigration detention facility in New Jersey, but when they arrived, he was not there. Khalil has reportedly been moved to a detention centre in Louisiana.

"This is a tactic that ICE loves to use, transferring someone to a facility that is further away from their legal assistance, community and loved ones," said Nathan-Pineau. "It increases the psychological strain of detention."

Greer has challenged Khalil’s detention, and a federal court is scheduled to hear the case on March 12.

But Palestinian rights advocates see Khalil’s arrest as part of a wider trend.

They say pro-Israel groups have long used allegations of anti-Semitism as a cudgel against pro-Palestine political expression, making little distinction between hateful prejudice and criticism of Israeli government policies.

"This arrest is an escalation, but it’s certainly not new," said Yousef Munayyer, a senior fellow at the Arab Center Washington DC.

"This is part of a pattern going back years, where pro-Israel groups have tried to find ways to penalise advocacy against Israeli policies through a combination of legal and extra-legal means."

He says those efforts include bills to ban participation in boycotts against Israel or adopt definitions of anti-Semitism that would include criticisms of Israel as evidence of prejudice.

Munayyer also pointed to the network of pro-Israel groups that target pro-Palestine academics, journalists, politicians and activists with public accusations of anti-Semitism.

In the aftermath of Khalil’s arrest, the pro-Israel group Canary Mission posted the names of five "suspected foreign nationals" with links to "campus extremism".

The Israeli government itself has been a firm supporter of those efforts and has sought to portray a variety of nonviolent protest methods as dangerous and anti-Semitic.

In 2022, for instance, Israeli President Isaac Herzog described a decision by the ice cream producer Ben and Jerry’s to end sales in Palestinian territories under Israeli military occupation as a "new form of terrorism".

Activists say that such efforts expanded during the most recent war in Gaza, with Democratic and Republican lawmakers calling for greater restrictions on pro-Palestine protests, which they say created an unsafe environment for Jews on school campuses.

Cases of harassment, abuse and violence against pro-Palestine protesters have received relatively scant attention by comparison.

"We need to remember what Mahmoud was harassed by Zionists and then arrested by DHS for. It was for protesting Israel's genocide of his own people, of the Palestinian people," said Miriam Osman, a 28-year-old organiser with the Palestinian Youth Movement, one of several groups that took part in a protest against Khalil’s arrest on Monday.

"And clearly, the Trump administration wants to criminalise any dissent of Israel's genocide, any dissent of the US’s role in it, and they're willing to roll back all of our rights to do that."

Others also worry that Trump’s crackdown on protesters will not remain limited to supporters of Palestine. He previously stated he would look to impose serious punishments on all "illegal protests", without defining what that entails.

"It’s important to note that Palestinians, Arabs and Muslims who are active in the fight for Palestinian rights are canaries in the coal mine," said Sahar Aziz, a professor at Rutgers Law School and author of the book The Racial Muslim.

"Americans should view how they are treated as an indicator of what’s in store for anyone who has views that dissent from the government."

With additional reporting from Joseph Stepansky