A federal judge has put a temporary halt to a proclamation by President Donald Trump, which sought to prevent foreign students from attending Harvard University in the U.S.

Trump’s announcement was part of the Republican administration’s ongoing efforts to stop the prestigious and affluent institution from admitting a significant number of international students, who contribute greatly to its research and scholarly work.

This is the second time within a month that incoming foreign students at Harvard have faced uncertainty due to policy changes, with the courts stepping in to provide relief. Alan Wang, a 22-year-old from China, who plans to begin his graduate studies at Harvard in August, expressed that the situation has been quite emotionally taxing.

“I cannot plan my life when everything keeps going back and forth. Give me some certainty: Can I go or not?” Wang said.

Wang was born and raised in China but attended college in the U.S. He’s now in China for summer vacation. Recently he has been exploring options in countries with more appealing immigration policies, including Canada, Australia and New Zealand.

Harvard filed a legal challenge on Thursday, asking for a judge to block Trump’s order and calling it illegal retaliation for Harvard’s rejection of White House demands. Harvard said the president was attempting an end-run around a previous court order.

A few hours later, U.S. District Judge Allison Burroughs in Boston issued a temporary restraining order against Trump’s proclamation. Harvard, she said, had demonstrated it would sustain “immediate and irreparable injury” before she would have an opportunity to hear from the parties in the lawsuit.

Burroughs also extended the temporary hold she placed on the administration’s previous attempt to end Harvard’s enrollment of international students. Last month, the Department of Homeland Security revoked Harvard’s certification to host foreign students and issue paperwork to them for their visas, only to have Burroughs block the action. Trump’s order this week invoked a different legal authority.

A court hearing is scheduled for June 16 to decide if the judge will extend the block on Trump’s proclamation.

If Trump’s measure were to survive the court challenge, it would block thousands of students who are scheduled to go to Harvard’s campus in Cambridge, Massachusetts, for the summer and fall terms. It would also direct the State Department to consider revoking visas for Harvard students already in the U.S.

“Harvard’s more than 7,000 F-1 and J-1 visa holders – and their dependents – have become pawns in the government’s escalating campaign of retaliation,” Harvard wrote Thursday in a court filing.

While the court case proceeds, Harvard is making contingency plans so students and visiting scholars can continue their work at the university, President Alan Garber said in a message to the campus and alumni.

“Each of us is part of a truly global university community,” Garber said Thursday. “We know that the benefits of bringing talented people together from around the world are unique and irreplaceable.”

Trump’s proclamation invoked a broad law allowing the president to block “any class of aliens” whose entry would be detrimental to U.S. interests. It’s the same basis for a new travel ban blocking citizens of 12 countries and restricting access for those from seven others.

In its challenge, Harvard said Trump contradicted himself by raising security concerns about incoming Harvard students while also saying they would be welcome if they attend other U.S. universities.

“Not only does this undermine any national security claim related to the entry of these individuals, it lays bare the Proclamation’s true purpose: to punish Harvard as a disfavored institution,” the school wrote.

Harvard has attracted a growing number of the brightest minds from around the world, with international enrollment growing from 11% of the student body three decades ago to 26% today.

Rising international enrollment has made Harvard and other elite colleges uniquely vulnerable to Trump’s crackdown on foreign students. Republicans have been seeking to force overhauls of the nation’s top colleges, which they see as hotbeds of “woke” and antisemitic viewpoints.

Garber says the university has made changes to combat antisemitism. But Harvard, he said, will not stray from its “core, legally-protected principles,” even after receiving federal ultimatums.

Trump’s administration also has taken steps to withhold federal funding from Harvard since it rejected White House demands related to campus protests, admissions, hiring and more. Harvard’s $53 billion endowment allows it to weather the loss of funding for a time, although Garber has warned of “difficult decisions and sacrifices” to come.

Associated Press writer Chrissie Thompson in Spokane, Washington, contributed to this report.

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The video in the player above is from an earlier report.