“The unanimity of federal court decisions on this issue should send a clear message to the executive branch that it cannot snatch people off the streets for peacefully protesting and put them in prison indefinitely,” said Elora Mukherjee, director of the Immigrants’ Rights Clinic at Columbia Law School. “The federal courts have unequivocally protected the First Amendment rights of the noncitizen protesters in these cases, literally across the country.”

Mr. Trump’s second term has been rife with similar efforts to suppress disfavored speech, as the administration bars news outlets from the Oval Office and cancels federal grants on the basis of words that its officials dislike. And while many of those efforts have been legally unsuccessful, it is difficult to measure their broader political effect.

In the case of the high-profile student protesters, if one of the president’s goals was to stifle the pro-Palestinian movement on college campuses, his administration has succeeded in some ways. The abrupt detention of foreign students may have had a profoundly chilling effect on international students, who could see Mr. Khalil’s monthslong detention as a warning.

“I am now regularly advising noncitizens to consider whether they want to engage in political speech,” Ms. Mukherjee said. “Of course, they should have a right to do so under the First Amendment, but there are potentially life-altering, devastating consequences for doing so.”

Mr. Khalil experienced those consequences firsthand. A Columbia University graduate student, he became one of the most recognizable faces of pro-Palestinian demonstrations on the school’s campus. He was arrested in March, detained and sent to Louisiana, where he was held for more than three months, missing his graduation and birth of his firstborn child.