The Trump administration on Friday abruptly moved to restore thousands of international students’ ability to study in the United States legally, but immigration officials insisted they could still try to terminate that legal status despite a wave of legal challenges.

The decision, revealed during a court hearing in Washington, was a dramatic shift by Immigration and Customs Enforcement, even as the administration characterized it as only a temporary reprieve.

The back and forth only contributed to the anxiety and confusion facing international students as the administration has moved to cancel more than 1,500 student visas in recent weeks.

On Friday morning, Joseph F. Carilli, a Justice Department lawyer, told a federal judge in Washington that immigration officials had begun work on a new system for reviewing and terminating the records of international students and academics studying in the United States. Until the process was complete, he said, student records that had been purged from a federal database in recent weeks would be restored, along with their legal status.

A senior Department of Homeland Security official, who spoke on the condition of anonymity, said the students whose legal status was restored on Friday could still very well have it terminated in the future, along with their visas.

The changes on Friday came amid a wave of individual lawsuits filed by students who have said they were notified that their legal right to study in the United States was rescinded, often with minimal explanation. In some cases, students had minor traffic violations or other infractions. But in other cases, there appeared to be no obvious cause for the revocations.