In an executive order signed Wednesday, Trump declared that it would jeopardize national security to allow Harvard to continue hosting foreign students on its campus in Cambridge, Massachusetts.

“I have determined that the entry of the class of foreign nationals described above is detrimental to the interests of the United States because, in my judgment, Harvard’s conduct has rendered it an unsuitable destination for foreign students and researchers,” Trump wrote in the order.

It’s a further escalation in the White House’s fight with the nation’s oldest and wealthiest university. A federal court in Boston blocked the Department of Homeland Security from barring international students at Harvard last week. Trump’s order invokes a different legal authority.

Trump invoked a broad federal law that gives the president authority to block foreigners whose entry would be “detrimental to the interests of the United States.” On Wednesday, he cited the same authority when announcing that citizens of 12 countries would be banned from visiting the U.S. and those from seven others would face restrictions. Trump’s Harvard order cites several other laws, too, including one barring foreigners associated with terrorist organizations.

In a statement Wednesday night, Harvard said it will “continue to protect its international students.”

“This is yet another illegal retaliatory step taken by the Administration in violation of Harvard’s First Amendment rights,” university officials said.

It stems from Harvard’s refusal to submit to a series of demands made by the federal government. It has escalated recently after the Department of Homeland Security said Harvard refused to provide records related to misconduct by foreign students.

Harvard says it has complied with the request, but the government said the school’s response was insufficient.

The dispute has been building for months after the Trump administration demanded a series of policy and governance changes at Harvard, calling it a hotbed of liberalism and accusing it of tolerating anti-Jewish harassment. Harvard defied the demands, saying they encroached on the university’s autonomy and represented a threat to the freedom of all U.S. universities.

Trump officials have repeatedly raised the stakes and sought new fronts to pressure Harvard, cutting more than $2.6 billion in research grants and moving to end all federal contracts with the university. The latest threat has targeted Harvard’s roughly 7,000 international students, who account for half the enrollment at some Harvard graduate schools.

“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 post 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 concerns.”

Rep. Pramila Jayapal, D-Wash., called the measure ridiculous and said it has nothing to do with national security.

“It’s a thinly veiled revenge ploy in Trump’s personal feud with Harvard, and continued authoritarian overreach against free speech,” Jayapal said on the social media site X.

The order applies to all students attempting to enter the United States to attend Harvard after the date of the executive order. It provides a loophole to allow students whose entry would “benefit the national interest,” as determined by federal officials.

Trump’s order alleges that Harvard provided data on misconduct by only three students in response to the Homeland Security request, and it lacked the detail to gauge if federal action was needed. Trump concluded that Harvard is either “not fully reporting its disciplinary records for foreign students or is not seriously policing its foreign students.”

“These actions and failures directly undermine the Federal Government’s ability to ensure that foreign nationals admitted on student or exchange visitor visas remain in compliance with Federal law,” the order said.

For foreign students already at Harvard, Secretary of State Marco Rubio will determine if visas should be revoked, Trump wrote.

The order is scheduled to last six months. Within 90 days, the administration will determine if it should be renewed, the order said.

A State Department cable sent last week to U.S. embassies and consulates said federal officials will begin reviewing the social media accounts of visa applicants who plan to attend, work at or visit Harvard University for any signs of antisemitism.

In a court filing last week, Harvard officials said the Trump administration’s efforts to stop Harvard from enrolling international students have created an environment of “profound fear, concern, and confusion.” Countless international students have asked about transferring from the university, Harvard immigration services director Maureen Martin said in the filing.