William Ayers, a former anti-war activist with ties to U.S. president-elect Barack Obama, said it seemed "a little absurd" Canadian officials denied him entry into Canada over the weekend.

William Ayers signs copies of his book at the All Souls Church in Washington in November. (Gerald Herbert/Associated Press)

Ayers, now a Chicago-based professor and author, was slated to deliver a speech at the University of Toronto's Centre for Urban Schooling but was barred from entering the country on Sunday night by border officials at the Toronto Island Airport.

"It seems slightly absurd and again, it's hard for me to speculate about what they were thinking. If it had been me, I would have let me in," Ayers told CBC's As It Happens.

Ayers — who once sat on the board of a charitable foundation with Obama and was recently pointed to by former Republican vice-presidential hopeful Sarah Palin as proof Obama had links to terrorism — said he had no idea why he was turned away, but that Canadian officials cited his arrest in 1969 during an anti-war demonstration.

"Well, they said I had an arrest record from 1969, and it's true that I was an anti-war activist and a civil rights activist and I have a long series of arrests, but they're all misdemeanours and they date back 40 years," he said.

A release issued by the Centre for Urban Schooling said Ayers was also not given the opportunity to meet with his lawyer.

Ayers said he has visited Canada more than a dozen times over the past 20 years, most recently last year. Aside from encountering some trouble crossing the border in the late 1960s, the University of Illinois-Chicago professor said he was only ever turned away on one other occasion three years ago.

"It seems to me a little absurd in the modern world to now start to think about borders in a kind of retrograde way. They are falling everywhere and the free exchange of ideas most of all, it seems to me, is something worth respecting and worth defending," Ayers said.

Canada Border Services Agency spokeswoman Anna Page told the Associated Press the agency couldn't comment on the case because of privacy laws.

She said there is a possibility that a person could be refused for their criminal history, regardless of whether it was serious or minor.

Ayers was the co-founder of the Vietnam War-era radical group the Weather Underground, which claimed responsibility for a series of bombings, including at the Pentagon and U.S. Capitol.

The human toll attributed to the Weather Underground, also known as the Weathermen, included a police officer killed and another badly hurt by a pipe bomb, two officers and a Brinks guard killed in an armoured truck robbery, and three radicals killed in a bomb-making accident.

Forty years after his involvement with the group, Ayers was thrown into the spotlight this summer when Palin said his work with Obama was evidence the then-presidential candidate was "palling around with terrorists." Ayers hosted a meet-the-candidate session for Obama at his home in the mid-1990s when Obama first ran for public office, but the two have had a limited relationship since then.

"My sense is that it was a profoundly dishonest narrative, it was one that I didn't think would work and in fact I'm very pleased it didn't work," Ayers said Monday of Palin's comments.

He said Obama's inauguration represents a huge and important shift in American politics, but that people shouldn't be looking to the president-elect to solve all the country's problems.

"He's not a monarch, he's a president in a democracy and we are all equal in that regard," Ayers said.

The professor, who was scheduled to meet with several students and teachers at the University of Toronto to discuss the role of education in a democracy, said he doesn't feel "haunted" by his previous activism, which took place at "at a time when the U.S. government was killing 2,000 people a month" in a "genocidal war," he said.

When asked if he would encourage his students to take the kind of action he did 40 years ago, Ayers said "absolutely not."

"I'm not a tactician, but what I do urge people to do, and I think it's a moral necessity and a requirement of citizenship, is to open our eyes and see what is before us. And then when we see things that are out of balance, unfair, unjust, we have a responsibility to speak up."

With files from the Associated Press