11/04/2015 05:10 EST | Updated 11/04/2015 06:59 EST

Mourad Benchellali, Former Gitmo Prisoner, Detained At Toronto Airport

"He said he came here to help Canada fight terrorism."

Former Guantanamo prisoner, Mourad Benchellali poses in Gennevilliers near Paris on May 13, 2015. Three months before September 11, 2001, Mourad Benchellali, aged 19, went to go to fight Jihad in Afghanistan, encouraged by his brother, a jihadist who served a severe sentence for having planned attacks in France. AFP PHOTO / FRANCOIS GUILLOT (Photo credit should read FRANCOIS GUILLOT/AFP/Getty Images)

TORONTO — A former Guantanamo Bay prisoner turned peace activist who was detained on arrival in Canada as an apparent national security threat will likely be allowed to return to France, his lawyer said Wednesday.

Mourad Benchellali, of Lyon, was being held as a maximum security prisoner after agents refused to allow him to withdraw his request to enter Canada and go home voluntarily.

"It looks like they changed their mind from what I just heard from them," lawyer Hadayt Nazami told The Canadian Press. "They're going to let him go."

Benchellali, 34, was expected to leave Canada as early as Wednesday night.

The French citizen, known for his deradicalization work, was detained at Toronto's international airport late Tuesday after arriving for a speaking tour. Immigration authorities indicated he was deemed to be a security risk.

"It's absurd. It really is absurd,'' Nazami said. "He said he came here to help Canada fight terrorism."

A spokeswoman with Canada Border Services Agency refused to comment.

"It is not a practice of the CBSA to confirm (or) deny whether a person has been detained," she said.

Benchellali has written about going to Afghanistan at the request of his older brother for several months in 2001. What he thought would be an adventure vacation turned out to be attendance at an al-Qaida training camp, according to his own account.

He was captured while trying to leave after the 9/11 terrorist attacks on the U.S., and turned over to American forces, who transferred him to Guantanamo Bay.

The Americans subsequently released him into French custody in July 2004. He and four others were convicted in 2007 in France of criminal association with a terrorist enterprise but the convictions were overturned in 2009.

"For a number of years he has been very active in the struggle against radicalization of the youth in France," Nazami said.

"From all the reports, his contribution has been very helpful to the authorities there."

According to Nazami, Canadian intelligence officials with the RCMP and CSIS cleared his five-day visit to Canada, which was to include a closed-door lecture to unspecified police and security people on deradicalization.

Nazami's visit was at the invitation of a Canadian film company, Stormy Nights Productions, which was making a documentary for the CBC. The company had arranged a series of meetings with professionals and young people in Montreal.

"I'm completely outraged," co-owner and producer Eileen Thalenberg said Wednesday.

"Mourad sent me a text saying, 'I never thought I'd be back in an orange (prisoner) suit again'."

Thalenberg said she spent until the early hours of Wednesday morning without success trying to get to talk to immigration officials or Benchellali at the airport.

Barring him makes no sense, she said.

One of the people in the documentary who was scheduled to meet with Benchellali was Canadian Christianne Boudreau whose son was killed in Syria, and who has now become a well-known activist for deradicalization.

"I feel terrible on his behalf to have to go through this, to have the nightmare start over again after he's been doing such amazing work in Europe,'' Thalenberg said.

"His voice is a necessary voice."

Benchellali, who according to his French lawyer is on an American "no fly" list banning him from flying in or over the United States, flew in via Iceland to avoid any problems.

"It's not a mistake: At the time of his detention, maybe CBSA didn't know all these facts but now they know and yet they will not allow him to come in,'' Nazami said.

The lawyer said a senior immigration would only say that the "grounds of his alleged inadmissibility are serious."

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