President Donald Trump has issued an order barring foreign students from entering the U.S. to study at Harvard University in an escalation of his fight with America’s oldest university.

The president said in a statement announcing the order Wednesday that he has also empowered Secretary of State Marco Rubio to begin revoking visas of foreign students at the Ivy League school.

The decision, Trump said in the statement, was made because the university refused to share information about “known illegal activity” committed by its international students.

The order came even though a federal judge in May issued an injunction blocking the administration from preventing Harvard from enrolling international students as part of the effort to punish the school for alleged antisemitism and civil rights violations. The university says it has been working to address those issues on its own.

“Admission to the United States to study at an “elite” American university is a privilege, not a right,” Attorney General Pam Bondi said in a statement on X. “This Department of Justice will vigorously defend the President’s proclamation suspending the entry of new foreign students at Harvard University based on national security.”

Harvard issued a defiant statement in response.

“This is yet another illegal retaliatory step taken by the administration in violation of Harvard’s First Amendment rights,” said the statement from spokesperson Jason Newton. “Harvard will continue to protect its international students.”

Trump’s fight with the university began in April, when Harvard refused to comply with White House demands to overhaul its admissions and disciplinary policies, alleging that they infringed on free speech rights. The White House responded by blocking more than $2 billion in federal grants.

In early May, Trump announced plans to cancel Harvard’s tax-exempt status. Later in the month, he floated redistributing $3 billion in university grants to trade schools.

International students make up roughly 27 percent of its student population at Harvard. The White House first pushed to revoke the university’s participation in the Student and Exchange Visitor Program — which allows universities to register foreign students — in late May. Harvard sued the Department of Homeland Security, and a federal judge issued a temporary injunction almost immediately.

U.S. District Judge Allison Burroughs said at a hearing last week that she planned to issue a preliminary injunction that would prevent the Trump administration from taking adverse action against Harvard while the litigation over the foreign student issue proceeds. She asked Justice Department and Harvard lawyers to try to agree on wording even though the Trump administration objects to any injunction. The two sides have yet to report back to the judge.