A federal judge halted on Friday the Trump administration’s attempts to block international students from attending Harvard University, the nation’s oldest university and one of its most prestigious.

Harvard had sued the Trump administration earlier in the day and less than 24 hours after the Department of Homeland Security moved to bar international students. Later Friday morning, at the university’s request, the Boston judge, Allison D. Burroughs, issued a temporary restraining order against the federal edict, agreeing that Harvard had shown that its implementation would cause “immediate and irreparable injury” to the university.

The administration action, and Harvard’s response, signified a dramatic escalation of the battle between the administration and Harvard. And the university’s forceful and almost immediate response served as evidence that stopping the flow of international students to Harvard, which draws some of the world’s top scholars, would destabilize the school.

In a letter to the Harvard community delivered Friday morning, Dr. Alan M. Garber, Harvard’s president, wrote, “We condemn this unlawful and unwarranted action,” adding that it “imperils the futures of thousands of students and scholars across Harvard and serves as a warning to countless others at colleges and universities throughout the country who have come to America to pursue their education and fulfill their dreams.”

Harvard University sued the Trump administration after it moved to block international students from enrolling.

The lawsuit, which accused the Trump administration of a “campaign of retribution” against the university, followed an announcement on Thursday that Harvard’s Student and Exchange Visitor Program certification had been revoked, halting the university’s ability to enroll international students.

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