A federal judge ordered the Trump administration on Friday to release Rumeysa Ozturk, a Tufts University student, saying that her continued detention could potentially chill “the speech of the millions and millions of individuals in this country who are not citizens.”

At a hearing at the Federal District Court in Vermont, the judge, William K. Sessions III, said Ms. Ozturk should be freed immediately: “Her continued detention cannot stand.”

Ms. Ozturk, a doctoral student from Turkey, has been in detention since March 25, when Immigration and Customs Enforcement agents in masks and plainclothes surrounded her outside her home in Somerville, Mass., while she was on the phone with her mother. She was put on a plane to a detention center in Louisiana, and her friends, family and lawyers didn’t know where she was for 24 hours, they said.

Her arrest led to public outrage at her treatment and criticism that the government is abusing the immigration system to deport international students. In seeking her release, her lawyers have accused the government of detaining her in retaliation for speech that is protected by the First Amendment. The main evidence against her appears to be an essay critical of Israel that she helped to write in a Tufts student newspaper last year.

They also said the conditions at the detention center were exacerbating her chronic asthma and preventing her from carrying out her academic work.

Her lawyer, Mahsa Khanbabai, said she was “relieved and ecstatic” that Ms. Ozturk had been released.

“When did speaking up against oppression become a crime?” Ms. Khanbabai asked. “When did speaking up against genocide become something to be imprisoned for?”

Ms. Ozturk appeared at the hearing by a remote feed from the ICE detention center in Basile, La., to the courtroom in Burlington, Vt. Ms. Ozturk, who is Muslim, wore a head scarf and an orange coverall.

A little over an hour into the hearing, she appeared to suffer an asthma attack, coughing and choking, and the judge allowed her to leave the feed for a while.

Ms. Ozturk testified that she had experienced escalating asthma attacks since her arrest. The first attack came when the plane that was taking her from Vermont to Louisiana stopped in Atlanta, she said.

A pulmonologist, Dr. Jessica McCannon, testified that Ms. Ozturk’s asthma was poorly controlled in detention and would continue to get worse if she were not released. She said that she had not been able to physically examine Ms. Ozturk but had spoken to her and reviewed her medical records.

The hearing had been expedited by Judge Sessions. Earlier this week, a federal appeals court ordered that she be transferred to Vermont by next week to attend a bail hearing. But Judge Sessions decided to hold the hearing with Ms. Ozturk still in Louisiana.

The hearing was held in Vermont because Ms. Ozturk had spent the night there in the custody of federal agents on the way to Louisiana, on a circuitous route that her lawyers said had prevented them from finding her.

Government lawyers in the appeals court hearing declined to discuss questions about speech raised by another judge. But Judge Sessions did not mince words on Friday, suggesting the government was trying to deport Ms. Ozturk based on the slenderest of evidence that she had posed a threat to American foreign policy interests.

“There has been no evidence that has been introduced by the government other than the Op-Ed,” he said in granting her release.

He added that noncitizens “may now avoid exercising their First Amendment rights for fear of being whisked away to a detention center from their home.”

Department of Homeland Security officials have said that Ms. Ozturk had “engaged in activities in support of Hamas, a foreign terrorist organization that relishes the killing of Americans.” And following her arrest, Secretary of State Marco Rubio commented on Ms. Ozturk’s detention at a news conference, saying that she had not been given a visa to “become a social activist that tears up our university campuses.”

But during the hearing Friday, the government’s lawyer, Michael Drescher, called no witnesses and hardly spoke. When he did speak, it was mainly to raise technical issues about the conditions of her bail.

Mr. Drescher asked the judge to bear in mind that even though Ms. Ozturk was being released from immigration custody, the deportation proceeding against her would continue.

Judge Sessions said Ms. Ozturk was free to return home to Somerville. He said he did not see any risk that she would flee. “She’s also free to travel to Massachusetts and Vermont as she sees fit” for further court appearances, he added.

The judge said he wanted to give Ms. Ozturk maximum mobility so she could pursue the educational opportunities that she needed to complete her doctorate.

Ms. Ozturk testified that she had been confined with 23 other women in a space intended for 14 people. Stress and the smells of cleaning supplies had exacerbated her asthma, she said. But when she sought treatment, the medical staff at the detention center had been condescending and had raised their voices at her, she said, and a nurse had ripped off her head scarf.

She testified that it was “impossible” to work on her dissertation in detention because she did not have access to her computer, professors, library or peers. Ms. Ozturk, who specializes in children’s media, is due to finish her doctoral dissertation in December and to graduate in February, according to the testimony.

Her adviser, Sara Johnson, testified that Ms. Ozturk had been doing innovative research on how adolescents used social media to benefit other people.

In describing her ties to the Tufts community, Ms. Ozturk said she had helped organize an event with colleagues where community members came together to express grief for children in conflict areas around the world, “from Gaza to Israel, from Russia to Ukraine, from Congo to Haiti, from Sudan to Yemen, from Cameroon to Afghanistan, from all parts of the world.”

The judge’s decision was another defeat for the government’s efforts to deport international students associated with pro-Palestinian advocacy. A week ago, a different federal judge in Vermont, Geoffrey W. Crawford, ordered the release of Mohsen Mahdawi, a Columbia student, from detention on bail.

Mr. Mahdawi is a permanent resident of the United States and is about to graduate from Columbia in May. His lawyers say that the government detained him in retaliation for his pro-Palestinian activism. He was arrested on April 14, after a naturalization interview at an immigration field office.