The Trump administration revoked Harvard University’s ability to enroll international students in its escalating battle with the Ivy League school, saying thousands of current students must transfer to other schools or leave the country.

The Department of Homeland Security announced the action Thursday, saying Harvard has created an unsafe campus environment by allowing “anti-American, pro-terrorist agitators” to assault Jewish students on campus. It also accused Harvard of coordinating with the Chinese communist party, saying it hosted and trained members of a Chinese paramilitary group as recently as 2024.

“This means Harvard can no longer enroll foreign students and existing foreign students must transfer or lose their legal status,” the agency said in a statement.

Harvard enrolls almost 6,800 foreign students at its campus in Cambridge, Massachusetts, accounting for more than a quarter of its student body. Most are graduate students, coming from more than 100 countries.

Harvard called the action unlawful and said it’s quickly working to provide guidance to students.

“This retaliatory action threatens serious harm to the Harvard community and our country, and undermines Harvard’s academic and research mission,” the university said in a statement.

The dispute stems from an April 16 request from Homeland Security Secretary Kristi Noem. The letter demanded that Harvard turn over information about foreign students that might implicate them in violence or protests that could otherwise lead to their deportation.

In a letter to Harvard on Thursday, Noem said the school’s sanction is “the unfortunate result of Harvard’s failure to comply with simple reporting requirements.”

Alison Frank Johnson teaches German history at Harvard. She says the move undermines Harvard’s academic and research mission.

“We’re talking here about students ... who’ve worked their whole lives to be able to attend a college of this caliber, who are looking forward to it, who’ve invested their own time, their families’ time, and money, into the institution. And now they don’t know if they can continue their educations,” Johnson told GBH News. “We’re also talking about graduate students who are working in labs to cure cancer.”