What does the law say?

Born in Syria to Palestinian refugees, Mahmoud holds a green card, which means he has lawful permanent residence status in the United States. This is different, however, from citizenship; green card holders can still be deported for certain serious crimes like fraud. But as of this writing, Khalil has not been charged with a crime. To justify the arrest, the Trump administration — including White House Press Secretary Karoline Leavitt and State Department officials — has cited a rarely-used provision of the Immigration and Nationality Act of 1952. It is the same statute used to justify Trump’s so-called “Muslim ban” in his first term. 

Section 237(a)(4)(C) of this act deems deportable any “alien whose presence or activities in the United States the Secretary of State has reasonable ground to believe would have potentially serious adverse foreign policy consequences for the United States.”

This means the Trump administration can push for Khalil’s deportation without a formal charge on the nebulous grounds of what it deems adversarial to US foreign policy. It remains to be seen what the government will decide is legitimate protest and advocacy versus what constitutes support for terrorism — or whether that will be made clear at all. For the Trump administration, there is a risk of maintaining this fuzzy boundary, however. A court could — and indeed a federal court has, in a previous case — find section 237(a)(4)(C), applied in deportation cases, “void for vagueness." 

What could case mean for future of immigration law, civil liberties? 

Should the Trump administration succeed, the case could redefine the boundaries of free expression for green card holders in the United States. If the use of section 237(a)(4)(C) stands, green card holders will face a new level of vulnerability, at risk of losing their legal protections over voicing opposition to US policy. 

More broadly, the case could erode the legal framework that safeguards free speech in the United States and could embolden officials to scrutinize and prosecute political activism based on alignment with US foreign policy. While the case directly concerns green card holders, it signals a potential shift in how all political expression is monitored and evaluated.

Zaha Hassan is a human rights lawyer and a fellow at the Carnegie Endowment for International Peace. “What we are seeing now is quite different — and dangerous. The speech of individuals already inside the United States is now being suppressed through different legal mechanisms, including the revocation of student visas or green cards,” she said in a Q&A session at Carnegie on Wednesday.

Whether or not the government wins its case against Khalil, his arrest has already had a chilling effect on speech. On Wednesday, the New York Times reported that administrators at Columbia University urged non-US citizen members of the faculty and students at its journalism school to avoid publishing work on Gaza, Ukraine and protests related to Khalil. They also warned those at the meeting against posting commentary on the Middle East on social media. Last week, Axios reported that the State Department is launching a program that uses AI to scan the social media activity of student visa holders, looking in particular for “terrorist sympathies.” 

Nathan J. Brown, a professor at George Washington University and senior fellow at Carnegie, said in the same event that on university campuses, “In recent years, allegations of antisemitism and Islamophobia have been handled by the Department of Education, generally as civil rights complaints. There have been complaints and counter-complaints, investigations and carefully negotiated settlements. What is happening now dwarfs that earlier activity. ... Criminal prosecution and expulsion are now replacing negotiated agreements as the instrument of choice.” 

What’s next for Mahmoud Khalil? 

After being detained, Khalil was transferred to custody in Louisiana and was issued a notice to appear before an immigration judge on March 27 for deportation hearings in the detention center where he is being held.

A day after Khalil's arrest, his lawyers filed a habeas corpus petition in a district court alleging that ICE’s arrest and detention of Khalil violates the due process clause and the First Amendment. A federal judge ruled on Monday that Khalil would remain in the United States throughout the proceedings in district court. This process will play out as a separate case from the deportation proceedings in the US immigration courts, which are not part of the regular federal court system and operate within the Department of Justice’s Executive Office for Immigration Review. Immigration courts are overseen by administrative law judges, who can be dismissed by Trump's attorney general, Pam Bondi.

His arrest has sparked demonstrations across US college campuses and beyond. Outside of the hearing Wednesday, thousands gathered to protest Khalil’s arrest.