The Department of Homeland Security said on Monday that it had deported a Brown University professor and doctor with a valid visa because they said she attended a Hezbollah leader’s funeral in February during a trip to Lebanon.

When questioned by Customs and Border Protection officers upon her return to the United States, Dr. Rasha Alawieh, who is Lebanese, “openly admitted” her support for the leader, Hassan Nasrallah, according to a Homeland Security spokeswoman. Dr. Alawieh was detained at Boston Logan International Airport on Thursday.

“A visa is a privilege not a right,” the spokeswoman, Tricia McLaughlin, said in a statement to The New York Times. “Glorifying and supporting terrorists who kill Americans is grounds for visa issuance to be denied. This is common-sense security.”

The department did not say how it knew that Dr. Alawieh had attended the funeral, which was held in a sports stadium and attracted tens of thousands of people. It also did not respond to questions about whether Dr. Alawieh has been accused of a crime or immigration violation.

Stephanie Marzouk, a lawyer representing a member of Dr. Alawieh’s family, did not respond to an interview request on Monday.

Late on Sunday, a team of lawyers from the firm of Arnold & Porter, who had been set to represent the family, withdrew from the case, telling the court their decision was made “as a result of further diligence.”

The federal judge overseeing the case decided to postpone a hearing in the case on Monday after Ms. Marzouk requested more time to prepare. She represents Dr. Alawieh’s cousin, Yara Chehab, who brought the case first to try to stop the government from deporting Dr. Alawieh, and then to seek her return to the United States.

Michael Sady, an assistant United States Attorney, filed a new motion in the case on Monday morning, according to the court docket. That filing and others have been sealed.

Dr. Alawieh, 34, is a Lebanese citizen who had traveled to her home country last month. She was detained on Thursday when she returned from that trip to the United States, according to a court complaint filed by Ms. Chehab.

The judge in the case, Leo T. Sorokin of the Federal District Court in Massachusetts, ordered the government on Friday evening to provide the court with 48 hours’ notice before deporting Dr. Alawieh. But at that time she was apparently already aboard a plane that was sitting on the tarmac in Boston, about to take off for Paris on her way to Lebanon.

According to the court docket, the government said on Monday that it was not aware of Judge Sorokin’s order when Dr. Alawieh’s plane took off. But Clare Saunders, one of the lawyers who was initially involved in the case, said in an affidavit filed over the weekend that she was at the airport Friday evening and had informed Customs and Border Protection officers of the judge’s order before the flight departed. Ms. Saunders is with Arnold & Porter, the firm that withdrew from the case on Sunday night.

Dr. Alawieh graduated from the American University of Beirut in 2015. Three years later, she came to the United States, where she held medical fellowships at the Ohio State University and the University of Washington, and then worked as a resident at Yale.

While she was in Lebanon visiting relatives, the American consulate issued her an H1-B visa, the kind for foreign workers with specialized skills. Before that, she had a J-1 visa, a type used by some foreign students.

A spokesman for Brown University, Brian Clark, said, “We continue to seek to learn more about what has happened.”

There is a shortage of American doctors working in Dr. Alawieh’s area of specialty, transplant nephrology. Foreign-born physicians play an important role in the field, according to experts.

Fear over immigration status could “harm the pipeline even more,” said Dr. George Bayliss, who works in the Brown Medicine kidney transplant program with Dr. Alawieh.

Her patients included individuals awaiting transplants and those dealing with the complex conditions that can occur after a transplant, Dr. Bayliss said. He called Dr. Alawieh “a very talented, very thoughtful physician.”

He also said he had not discussed politics with her.

In a letter on Sunday to members of the university community, Brown’s administration advised foreign students to “consider postponing or delaying personal travel outside the United States until more information is available from the U.S. Department of State.”

Maya Shwayder contributed reporting. Susan C. Beachy contributed research.