Detained outside his home and flown across the country to face deportation, US permanent resident Mahmoud Khalil's case is shaping up to be a fresh test of the limits of Donald Trump's administrative power.
Since returning to the White House in January, the returned commander-in-chief has faced numerous challenges and court hearings over his agenda.
But the student protester's case will be a complex one, as the US government tries to cancel his permanent residency using a Cold War-era law that could have free-speech implications.
Here's what to know about the detention of Mahmoud Khalil.
Who is Mahmoud Khalil?
Born in Syria and of Palestinian heritage, Mr Khalil first entered the US on a student visa in 2022 to pursue a Masters in Public Administration at Columbia University.
In 2023, he married US citizen Noor Abdalla, and in 2024, he received a green card, making him a permanent resident of the US.
He completed his masters degree in December 2024.
While a student, Mr Khalil participated in student action protesting Israeli military action in Palestine and demanding Columbia University divest from economic and academic stakes in Israel.
He became a prominent participant in the protests, acting as the lead negotiator between the university and student groups.
It's his participation in these protests that has drawn the focus of the Trump administration.
They've accused him of siding with Hamas terrorists and spreading antisemitism — claims denied by Mr Khalil's lawyers.
Despite not being accused of any crimes, Mr Khalil has been arrested and detained thousands of miles from his home.
Trump's focus on student protesters
During his election campaign, Donald Trump promised to clamp down on pro-Palestinian protests occurring on college campuses.
That included by pulling federal funding from universities unless they cracked down on such activity, and by revoking student visas of non-citizen protesters.
On January 29, soon after taking office, Mr Trump began moving to fulfil that vow.
He issued an executive order to combat antisemitism, "using all available and appropriate legal tools, to prosecute, remove, or otherwise hold to account the perpetrators".
It included a clause requiring universities to monitor for and report activity by immigrant students and staff that could lead to investigations, and if warranted, deportation.
Here, Columbia University — and by extension, Mr Khalil — found itself in the crosshairs.
The school had been the location of the most prominent student-led pro-Palestine protests in 2024, because students had illegally set up encampments and occupied a campus building, Hamilton Hall.
Mr Khalil was not accused of taking part in the Hamilton Hall takeover.
He had been suspended by the university before the building was occupied by students, accused of refusing to leave the encampment on campus lawns, but was quickly reinstated.
But despite having no criminal allegations to level against Mr Khalil, the Trump administration detained him.
What happened to Mahmoud Khalil?
After the Trump administration flagged its intention to pursue student protesters, some X accounts began circulating videos of Mr Khalil at the demonstrations.
Some referenced his role as a leading figure in the campus protests and others accused him of organising events where pro-Hamas pamphlets were distributed, an accusation repeated by the White House — Mr Khalil's lawyers have denied he sided with Hamas.
Many tagged Secretary of State Marco Rubio, calling for his arrest and deportation.
According to court filings, Mr Khalil arrived at his apartment building with his heavily pregnant wife on March 8, where they were approached by four men in plain clothes.
The group identified themselves as being with the Department of Homeland Security.
Asked whether they had a warrant, the agents claimed to have one on a phone but, it was alleged in court filings, never showed it to Mr Khalil.
They asserted they were detaining him because his student visa had been revoked, despite Mr Khalil being a permanent resident, and therefore not on a student visa at the time.
When informed of this over the phone by Mr Khalil's attorney, Amy Greer, one agent said his green card had been revoked too.
He said Mr Khalil would be detained in Manhattan, but when Ms Greer began to ask more questions, the agent hung up on her, and refused to allow Mr Khalil to speak with her again.
What has Khalil said?
At 3am on the night of his arrest, Mr Khalil's lawyer Amy Greer filed a habeas corpus protest in New York, where he was being held.
That's a legal filing that alleges a detainee has been illegally arrested and requests to have law enforcement authorities explain the grounds for incarceration.
In it, she said the detention of Mr Khalil violated his constitutional rights, as well as several other laws.
She argued the government was attempting to deport him in retaliation to his First Amendment-protected speech.
The First Amendment prohibits the government from censoring speech.
It generally means people can't be criminally punished for things they say, even if it's offensive or outrageous.
A notorious example of this is the Supreme Court's 2011 ruling that the Westboro Baptist Church had a right to picket soldiers' funerals "to communicate its belief that God hates the United States for its tolerance of homosexuality".
Ms Greer also said Mr Khalil's Fifth Amendment right to due process had been violated.
That section of the Constitution requires the government to follow fair legal procedures when detaining detaining someone.
It means Mr Khalil:
- Must receive written notice for the legal and factual grounds for his removal
- Must be given a hearing before the Immigration Court
- Is entitled to an attorney
- Must be permitted to see and refute the evidence before him
Generally, the First and Fifth Amendments do not discriminate between citizens and non-citizens, so Mr Khalil should still be protected, even if he is only a permanent resident.
On Tuesday, he released a letter from detention, dictated over the phone to his family.
"My arrest was a direct consequence of exercising my right to free speech as I advocated for a free Palestine and an end to the genocide in Gaza, which resumed in full force on Monday night," the statement reads.
"The Trump administration is targeting me as a part of a broader strategy to suppress dissent.
"Visa-holders, green-card carriers, and citizens alike will all be targeted for their political beliefs."
Why does the Trump administration say it can deport him?
The US government is yet to file legal documents which state their ground for attempting to deport Mr Khalill.
Comments by Mr Rubio and White House Press Secretary Karoline Leavitt suggest the White House will attempt to justify his arrest under a provision of the Immigration and Naturalization Act of 1952.
Section 1227 of that law states the secretary of state can declare someone "deportable" if they have "reasonable ground to believe" the visa-holder engaged in activity "subversive to the national security" or that would have "potentially serious adverse foreign policy consequences".
But the same statute states an immigrant can't be deported if their beliefs or statements would be lawful in the US.
At this stage, the government has not provided any evidence suggest Mr Khalil broke any laws in the US.
Whatever the Immigration and Naturalization Act says, it can't be used to override constitutional freedoms.
That's because the Constitution takes priority over all other laws in the US, according to its Supremacy Clause.
We've even seen this clause tested in many cases over the years, where the Supreme Court has largely held the interpretation that lower courts and laws can't override constitutional rights.
Has a case like this happened before?
Legal experts say the provision has been tested just once before.
That was in 1995, when the statute was used to detain Mario Ruiz Massieu, a former deputy attorney-general of Mexico, who was facing an arrest warrant in the South American nation.
Then-secretary of state Warren Christopher argued returning Mr Massieu was important to maintaining cooperation between the US and Mexico.
Massieu challenged the move in a case that was overseen by Maryanne Trump Barry, Donald Trump's eldest sister.
She refused to deport Mr Massieu, arguing the language of Section 1227 was not clear about what conduct was deportable.
"No-one outside the Department of State and, perhaps, the president ever knows what our nation's frequently covert foreign policy is at any given time,” she wrote in her ruling.
"Thus, there is no conceivable way that an alien could know, ex-ante, how to conform his or her activities to the requirement of the law.
"Of course, it is even less likely that an alien could know that his or her mere presence here would or could cause adverse foreign policy consequences when our foreign policy is unpublished, ever-changing, and often highly confidential."
She concluded the statute was unconstitutionally vague and violated Mr Massiue's Fifth Amendment right to due process.
The administration of former President Bill Clinton appealed the ruling and it was reversed on a technicality that did not address the law's constitutionality.
Looking even further back in time, we can find a case that appears more similar to Mr Khalil's: that of Australian-born trade union leader Harry Bridges.
The US government attempted to deport Mr Bridges under a different law in 1945, accusing him of being a communist and arguing such ties made him ineligible to remain in the country.
But the Supreme Court concluded the mere association with a political ideology without evidence of illegal action was not grounds for removal.
The opinion published on the case emphasised that the First Amendment made "no exception in favour of deportation laws".
"Harry Bridges has done no more than exercise his personal right to free speech and association," Supreme Court Justice Frank Murphy wrote.
"Yet, upon proof of that fact, he would be subject to deportation under the statute. The invalidity of legislation of such nature is inescapable."
But courts have also allowed the government to deport non-citizens based on their political affiliations in the past.
In the 1952 case of Harisiades v Shaughnessy, the Supreme Court upheld the deportation of a group of immigrants who were Communist Party members.
They argued communism was inherently an endorsement of violent revolution.
Where is Mahmoud Khalil now?
At the LaSalle Detention Center in Jena, Louisiana.
Louisiana has been a popular state for the Trump administration to detain people facing deportation.
He and his lawyer are arguing his case should be heard in the southern district of New York, where he resides and was arrested.
But the Trump administration says it should be held in Louisiana, where he is currently being held, or dismissed entirely.
The government was able to move the case out of the southern district of New York's jurisdiction, because Mr Khalil's attorney filed the habeas corpus protest requesting he be kept in New York after he had already been whisked out of state.
That's despite his attorneys saying they had no way of knowing at the time that he had been moved in order to file the protest in the correct jurisdiction, with the ICE database still showing Mr Khalil's location as being in New York.
Where does the case go from here?
Mr Khalil's legal team has now filed an amended habeas corpus protest on his behalf, and a judge has temporarily blocked Mr Khalil's deportation.
Immigration lawyer David Leopold told Reuters the Trump administration had likely overstepped its statutory authority, and its use of the Immigration and Naturalization Act of 1952 was vulnerable to being overturned in court.
But the question of whether the government breached Mr Khalil's constitutional rights will be answered down the line.
First, it must be decided which court will hear the case, and it appears Mr Khalil will remain detained in Lousiaina until then.
