The Trump administration has revoked Harvard University’s Student and Exchange Visitor Program certification, effectively halting the university’s ability to enroll international students. Department of Homeland Security Secretary Kristi Noem announced the decision in a letter to Harvard President Alan M. Garber, stating that the certification is revoked “effective immediately.”

The move comes after a back-and-forth between Harvard and the White House over the legality of a records request as part of the Department of Homeland Security’s investigation. Noem alleged that Harvard’s submission of disciplinary records was “insufficient” and failed to address “simple reporting requirements.”

“We are fully committed to maintaining Harvard’s ability to host international students and scholars, who hail from more than 140 countries and enrich the University—and this nation—immeasurably,” a Harvard spokesperson said. “This retaliatory action threatens serious harm to the Harvard community and our country, and undermines Harvard’s academic and research mission.”

The decision affects over 6,000 international students currently enrolled at Harvard, many of whom attend on F-1 or J-1 visas. Current international students may have to transfer, change their immigration status, or leave the country.

Noem stated that Harvard’s actions “perpetuate an unsafe campus environment that is hostile to Jewish students, promotes pro-Hamas sympathies, and employs racist ‘diversity, equity, and inclusion’ policies.” Harvard has denied these allegations.

The university is likely to challenge the decision in court. “This is devastating,” said Leo Gerdén, an international student from Sweden. “Harvard needs to fight the DHS decision as hard as we possibly can.”