WASHINGTON (AP) — The arrest of a Palestinian activist who helped organize campus protests of the war in Gaza has sparked questions about whether foreign students and green card holders are protected against being deported from the U.S.

Mahmoud Khalil was arrested Saturday by Immigration and Customs Enforcement agents. Homeland Security officials and President Donald Trump have indicated that the arrest was directly tied to his role in the protests last spring at Columbia University in New York City.

Khalil is being held at an immigration detention center in Jena, Louisiana, while he awaits immigration court proceedings that could eventually lead to him being deported. His arrest has drawn criticism that he’s being unfairly and unlawfully targeted for his activism while the federal government has essentially described him as a terrorist sympathizer.

A look at what kind of protections foreign students and green card holders have and what might be next for Khalil:

Can someone with a green card be deported?

A green card holder is someone who has lawful permanent residence status in the United States.

Jaclyn Kelley-Widmer is a law professor at Cornell Law School who teaches immigration law. She said lawful permanent residents generally have many protections and “should be the most protected short of a US citizen.”

But that protection isn’t absolute. Green card holders can still be deported for committing certain crimes, failing to notify immigration officials of a change in address or engaging in marriage fraud, for example.

The Department of Homeland Security said Khalil was taken into custody as a result of Trump’s executive orders prohibiting antisemitism.

Trump has argued that protesters forfeited their rights to remain in the country by supporting the Palestinian group Hamas, which controls Gaza and has been designated 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.

Experts say that officials seem to indicate with their rhetoric that they are trying to deport Khalil on the grounds that he’s engaging in some sort of terrorist activity or somehow poses a threat.

Khalil has not been convicted of any terrorist-related activity. In fact, he has not been charged with any wrongdoing.

But experts say the federal government has fairly broad authority to arrest and try to deport a green card holder on terrorism grounds.

Under the Immigration and Nationality Act, green card holders do not need to be convicted of something to be “removable,” Kelley-Widmer said. They could be deported if the secretary of homeland security or the attorney general have reasonable grounds to believe they engaged in, or are likely to engage in, terrorist activities, she said.

But Kelley-Widmer said she’s never seen a case where the alleged terrorist activity happened in the U.S., and she questioned whether taking part in protests as Khalil did qualifies.

What did ICE say about why they were arresting him?

One of the key issues in Khalil’s case is what ICE agents said to his lawyer at the time he was arrested.

His lawyer, Amy Greer, said the agents who took him into custody at his university-owned home near Columbia initially claimed to be acting on a State Department order to revoke his student visa.

But when Greer informed them that Khalil was a permanent resident with a green card, they said they would revoke that documentation instead.

Kelley-Widmer said that exchange raises questions about how familiar the agents who arrested him were with the law or whether there was a “real disregard for the rule of law.”

“I think we should be really concerned that this is happening,” she said.

What are the next steps in his case?

Secretary of State Marco Rubio said in a message posted Sunday on X that the administration will be “revoking the visas and/or green cards of Hamas supporters in America so they can be deported.”

If someone is in the country on a student visa, the State Department does have authority to revoke it if the person violates certain conditions. For example, said Florida immigration attorney John Gihon, it’s quite common for the State Department to cancel visas of foreign students who get arrested for drunk driving.

But when it comes to someone who’s a lawful permanent resident, that generally requires an immigration judge to determine whether they can be deported.

Gihon said the next step is that Khalil would receive charging documents explaining why he’s being detained and why the government wants to remove him, as well as a notice to appear in immigration court.

Generally, he should receive those within 72 hours of being arrested, and then he would make an initial appearance before an immigration judge. That could take from 10 days to a month, Gihon said.

But he cautioned that right now he’s seeing extensive delays across the immigration court system, with clients often moved around the country to different facilities.

“We are having people who are detained and then they’re bounced around to multiple different detention facilities. And then sometimes they’re transferred across the country,” he said.

Khalil’s lawyers have also filed a lawsuit challenging his detention. A federal judge in New York City ordered that Khalil not be deported while the court considered his case. A hearing is scheduled for Wednesday.