American voters largely shrugged off attempts during last year’s presidential campaign to portray Bill Ayers, the former antiwar militant who teaches at the University of Illinois at Chicago, as a terrorist. Canadian border officials apparently still have some issues with the education professor.

According to The Globe & Mail, a Toronto newspaper, the Canada Border Services Agency declared him inadmissible at the Toronto City Centre Airport on Sunday evening, forcing him to cancel a planned speech at an education conference.

Mr. Ayers had been scheduled to speak tonight to a research group at the University of Toronto, the Centre for Urban Schooling and the Secondary Program: Inner City Education. In a statement on its Web site, the center said that organizers were “shocked” and “extremely disappointed” by the border agency’s actions, and that the event would be rescheduled.

In remarks to The Globe & Mail, Jeffrey Kugler, the center’s executive director, called the refusal to allow Mr. Ayers into the country a violation of academic freedom. “There is no one who could have thought it possible there was any danger to Canadians to letting him in,” Mr. Kugler said. —Charles Huckabee

Update (1/21): The Canadian Association of University Teachers has released an open letter to Prime Minister Stephen Harper that says it is wrong for the government to decide whom universities may invite to speak on their campuses.