In protest of President Donald Trump’s immigration ban, 14 University of Minnesota professors have signed an open letter saying they will boycott international conferences held in the U.S. for the foreseeable future.

The letter was written by an international collective of academics to protest the ban, which many academics claim inhibits their peers from attending important conferences. Over 6,400 academics have signed the letter thus far.

Nadine El-Enany, a professor at Birkbeck Law School, and a contributor to the letter, said the petition is both a way for professors to abstain from benefits denied to their peers and to “clearly indicate in a very practical way that our business, as educators, cannot go on as normal while such an emergency is taking place.”

El-Enany said the open letter has already led to results. Conference organizers have withdrawn from Stanford’s Law, Culture and Humanities conference, and El-Enany believes the petition has the potential to pressure other academic institutions to question the immigration ban.

El-Enany said ideally, professors would continue to boycott conferences despite the fact that the ban was ruled against by the U.S. Ninth Circuit Court of Appeals earlier this month.

“The situation in the U.S. risks getting worse for all nationals of Muslim-majority countries, academic or not, if there’s not strong resistance now,” she said.

University of Minnesota professor of pharmacology Ameeta Kelekar said the ban threatens the free exchange of ideas in the sciences.

“We will not just have lost the support of scientists from the Middle Eastern and African countries affected by the ban, but the support, trust and respect of the entire international scientific community as well,” Kelekar said.

Charles Rogers, a family medicine and community health professor at the University, said he signed the petition in support of international students — who make up over a quarter of the student population — as well as professors.

Maria Saqui-Salces, a professor of gut cellular physiology at the University, said the ban worries her on a professional and personal level.

“I am an immigrant myself, and even when my country of citizenship is not included in the ban, you always have to wonder,” she said. “If this executive order gets ‘accepted,’ what country comes next in the ‘not welcome’ list?”

Signing the petition, she said, was a way for her to speak up, given she wasn’t able to vote in the election.

“I live here, work here and pay taxes,” she said. “But I don’t vote obviously, and I don’t get much of a say in any way of government decision if not by means of open letters.”

In addition to signing the open letter, University professors Barbara Frey and Evelyn Davidheiser drafted a separate letter to University President Eric Kaler and Provost Karen Hanson demanding the University take a stronger stance against the ban.

Though Kaler issued a statement about Trump’s order at the end of January, University Spanish and Portuguese studies professor Mary Pogatshnik said some faculty believed Kaler’s statement was “vague and incomplete,” and that he and the University should issue a new statement.

Hanson’s office has since responded to the letter, asking faculty members for recommendations on how the University should respond.