On Monday, Peter Herman, a professor of electrical and computer engineering at the University of Toronto, found himself taking the place of one of his graduate students at an academic conference in San Francisco.
Ehsan Alimohammadian, an international PhD student from Iran, was supposed to deliver the results of his research. Instead, he never set foot at the conference. After being detained for more than 10 hours in the San Francisco airport, Mr. Alimohammadian could not enter the United States, one of thousands of scholars affected by the immigration ban imposed on citizens of seven countries this past Friday through an executive order signed by U.S. President Donald Trump.
"This was his turn to be introduced to the world," Dr. Herman said. "He is the one who should be getting the attention."
Dr. Herman decided to present his student's paper, but prefaced it by expressing his opposition to a policy that he believes prevents the free expression of ideas.
Academics have been among the most vocal protesters of the immigration ban. Under the policy, citizens of seven countries – and all refugees – are temporarily barred from entering the United States. Dual citizens of Canada are exempt from the order, but scholars from the seven countries studying or teaching here on a visa cannot enter the U.S.
Now, a growing number of academics are calling for stronger action than street protests or calls to MPs and American lawmakers. They want to see a boycott of academic conferences in the United States.
Boycotts have a long and controversial academic history. Some of those hurt can be other scholars, even those the boycott is trying to help. That was an allegation levied at the long academic boycott waged against South African apartheid. More recently, there have been acute disagreements among academics on moves to boycott events in Israel.
What is unusual about the latest debate is how quickly the calls to strike the U.S. off research and exchange trips have gathered support. As of Tuesday afternoon, more than 4,000 academics around the world signed a petition calling for a boycott of international conferences held in America.
"I … acted in solidarity with citizens and scholars of the countries, students and academics banned from entering the United States," said Cristina Rojas, a professor of political science at Carleton University.
Dr. Rojas, who studies citizenship, is one of hundreds of Canadian professors who added their name to the petition.
For Dr. Rojas, the debate has practical implications. In February, the International Studies Association (ISA) is holding its annual conference, one of the world's largest scholarly gatherings for social scientists, in Baltimore.
ISA has come under sustained criticism for not strongly denouncing the Trump ban. In the end, Dr. Rojas decided to attend.
Going will "further the internal discussion," she said.
Other professors who signed the call for a boycott have similarly mixed feelings.
"I think the primary role of the boycott, especially if influential scholars refuse to travel, is to make all of us aware of the fact that this travel ban is having an impact on who can and cannot take part in an essential part of our academic life," said Marie-Eve Morin, an associate professor of philosophy at the University of Alberta. "What we don't want is for academic life to go on as usual. That would erase the bodies and voices of those who cannot be there."
But some professors believe the boycott will not hurt Mr. Trump's administration.
"If you boycott academic conferences, you are doing Trump's work: silencing critical voices and isolating the U.S. Why organize a protest that aids the very man you're trying to undermine?" said Loren Landau in an e-mail interview. Dr. Landau is the director of the African Centre for Migration and Society at the University of Witwatersrand in Johannesburg.
The academic boycott of South Africa may have contributed to delegitimizing the apartheid-era government, he added, but it also hurt South African scholars.
For his part, Mr. Alimohammadian, who prepared for months to deliver his paper, said he has no interest in going to the United States for the time being.
"Most of the border guards were very nice," he said. "They were very sorry and they tried to help me, but they were just doing their job." But the experience made him feel that he is not welcome south of the border. "Why should I try again?"