An American education professor, one of the founders of a radical 1960s group known as the Weather Underground, which was responsible for a number of bombings in the United States in the early 1970s, was turned back at the Canadian border last night.

Dr. William Ayers, a professor of education at the University of Illinois-Chicago and a leader in educational reform, was scheduled to speak at the Centre for Urban Schooling at University of Toronto's Ontario Institute for Studies in Education. But that appearance has now been temporarily cancelled.

"I don't know why I was turned back," Ayers said in an interview this morning from Chicago. "I got off the plane like everyone else and I was asked to come over to the other side. The border guards reviewed some stuff and said I wasn't going to be allowed into Canada. To me it seems quite bureaucratic and not at all interesting ... If it were me I would have let me in. I couldn't possibly be a threat to Canada."

"The entire four or five hours he was not allowed to have representation at all. To me this is an issue of academic freedom. He could not be a threat to anyone ever. Anyone who knows anything about this man – he's a distinguished scholar at the University of Illinois and he has been involved in education reform over the past 15 years. To imagine in any way he was a threat to Canada is really absurd."