Omar Khadr, a 26-year-old Canadian, had been in the U.S. detention camp in Cuba's Guantanamo Bay since 2002. On Sept. 29, 2012, the U.S. flew him from Guantanamo and he is now in prison in Canada.

Following a plea deal with prosecutors in October 2010, it was initially anticipated that Khadr could return to Canada in November 2011, after which he would be able to apply for parole.

Khadr came to Guantanamo nine months after it opened as a temporary facility in 2002. He was captured by U.S. forces in Afghanistan earlier that year — at the age of 15 — and detained on suspicion of killing a U.S. soldier during a firefight.

Khadr has been held in maximum-security Millhaven Institution in Bath, Ont., since he was returned to Canada. He will appeal his plea-bargained guilty plea and war crimes convictions in a U.S. civilian federal court, his Canadian lawyer told CBC News on April 27, 2013.

Khadr's charges, according to his lawyer, Dennis Edney, "are not recognized international law–of–war offences. We questioned the validity of the charges before the Military Commission Process."

The charge of murder in violation of the law of war is "particularly offensive and not recognized by any legal observers outside the commission process," Edney said. "We expect the military tribunal convictions will be overturned considering the present state of the law and ultimately putting to rest the Harper government's characterization of Omar Khadr as a war criminal and a terrorist."

Khadr's U.S. lawyer expects the U.S. Court of Appeals for the District of Columbia Circuit to overturn Khadr's convictions based on two previous rulings where two of Osama bin Laden's aides who were convicted at Guantanamo later saw their terrorism convictions overturned.

What are the key terms of the plea deal?

Under the plea deal revealed during his trial at Guantanamo Bay, Khadr pleaded guilty to the murder of Sgt. 1st Class Christopher Speer and to four other charges: murder in violation of the law of war, attempted murder in violation of the law of war, conspiracy, providing material support for terrorism, and spying.

Khadr agreed not to be part of any lawsuit against the U.S. or to enter the country after his transfer to Canadian custody or to profit from any publication of his story.

Khadr listens to taped testimony near the end of his sentencing trial at Camp Justice, in Guantanamo Bay, Cuba, on Oct. 31, 2010. Khadr was sentenced to eight more years in custody under a plea agreement after a military sentencing jury said he should serve 40 years for war crimes. This sketch was reviewed by the U.S. Department of Defence. (Sketch by Janet Hamlin, Pool/Associated Press)

He agreed to a sentence of eight years, with no credit for time served, with the first year spent in U.S. custody.

The U.S. agreed "to support transfer of the accused" to Canadian custody if he stuck to the plea agreement.

Was Canada required to accept Khadr's return?

The government was not party to the plea deal, nor was it required to consent to Khadr's transfer to Canada.

However, in an exchange of diplomatic notes between the U.S. Department of State and Canada's Department of Foreign Affairs on Oct. 23, 2010, Canada said it "is inclined to favourably consider Mr. Khadr's application to be transferred to Canada."

Then Foreign Minister Lawrence Cannon clarified the government's role when he told the House of Commons the following week that his government "will implement the agreement between Mr. Khadr and the government of the United States."

Khadr arrived at the U.S. detention facility at Guantanamo Bay in October 2002. This photo shows detainees sitting in a holding area watched by military police at Camp X-Ray inside the base on Jan. 11, 2002, the day the prison was officially opened. (Shane T. McCoy/U.S. Department of Defence/Reuters)A year later, the Minister of State of Foreign Affairs Diane Ablonczy confirmed during question period that her government, "will respect the agreement between Omar Khadr and the U.S. government."

Although U.S. President Barack Obama has not delivered on his promise to close the detention centre at Guantanamo Bay, his government does want to reduce the number of prisoners held there and is not likely to look favourably on Canada refusing to accept Khadr.

About a year after the plea deal, The Toronto Star's Michelle Shephard, author of Guantanamo's Child, a book on the Khadr case, reported that a Pentagon official told her, "'We'd drop him off at the border if we could.'"

How are transfers carried out?

Canada has treaties with about 80 countries, including the U.S., for the transfer of offenders back to their own country.

The first step, an application for transfer by the applicant to the Canadian government, has happened, and now, the International Transfer of Offenders Act governs the process.

It's not unusual for the Canadian government to take months to approve a transfer, according to retired Canadian diplomat Gar Pardy, who has extensive experience with such transfers.

Gar Pardy, a former Canadian diplomat seen in this June 2, 2005, photo, was first involved with issues related to the Khadr family in 1996. (Jonathan Hayward/Canadian Press)

Pardy told CBC News that the directions given by the ministers involved — public safety, justice, the attorney general and the prime minister — could also affect the timing but "these are political decisions, not legal ones."

How will Khadr spend his sentence in Canada?

Khadr was being held under maximum security at Guantanamo.

The authorities at the Canadian facility in Bath, Ont., where he serves his time determine the security level at which he is confined.

Is the Youth Criminal Justice Act relevant in Khadr's case?

Khadr was 15 when he was arrested, but according to University of Toronto law professor Audrey Macklin, because he was given a sentence of more than seven years, his sentence "cannot be regarded under the young offenders regime" and is treated as an adult sentence.

She believes Khadr's eight-year sentence was "calculated to deny him any access to being treated as a young offender."

Further complicating matters for the Canadian legal system is that Khadr was not charged with first-degree murder but a war crime of murder. Macklin notes that that crime "doesn't actually exist in the international lexicon of war crimes." Khadr is the only person in the world convicted of that war crime.

When Omar Khadr, seen here when he was nine years old, lived with his family in Pakistan, his father, Ahmed, was being held by Pakistani authorities. Khadr met Canadian Prime Minister Jean Chrétien, who was visiting Pakistan in January 1996. Chrétien asked Pakistani Prime Minister Benazir Bhutto to ensure Ahmed received a fair trial. (CBC)

However, the Youth Criminal Justice Act could influence the transfer in a process that requires the Canadian government to determine what the sentence is going to be prior to the transfer.

Though an administrative process, officials in the Public Safety Ministry determine what an equivalent Canadian sentence would be, according to Canadian law. The officials could look at the Criminal Code and/or the Youth Criminal Justice Act when making that assessment.

Pardy doubts the Harper government would allow the officials to use the Youth Criminal Justice Act but sees possible grounds for Khadr's lawyers to argue in court that the act should be considered.

What is the impact of the Supreme Court ruling on the Khadr case?

In January 2010, the Supreme Court of Canada ruled that Canadian officials contributed to the violation of Khadr's rights to life, liberty and security of the person. The court concluded that bringing Khadr back to Canada would stop the violation of his rights by preventing him from facing trial.

A statue outside the Supreme Court of Canada overlooks the Peace Tower on Parliament Hill in Ottawa on Jan. 29, 2010. That day, the court ruled that Khadr's Charter rights had been violated but did not order his repatriation from Guantanamo Bay. (Pawel Dwulit/Canadian Press)

The court also ruled that ordering the government to demand Khadr's repatriation was not a suitable remedy because of the government's constitutional responsibility to make decisions on matters of foreign affairs.

Lawyer David Harris, a former chief of strategic planning at the Canadian Security Intelligence Service (CSIS), sees the ruling as offering Khadr a "significant benefit" once he is back in Canada.

The court found that Khadr's interrogation by Canadian officials "offends the most basic Canadian standards about the treatment of detained youth suspects."

Harris said Khadr's lawyers could argue that his guilty plea "from the perspective of Canadian constitutional law, is not to be respected." They will say that it is "fruit of a poison tree, not to be eaten by the Canadian government or our courts."

For Pardy, the Supreme Court ruling means the government can pick and choose which Canadians in distress abroad it helps.

"You've got discrimination of the worst kind, and they can get away with it because of that Supreme Court decision."

Is the Convention on the Rights of the Child relevant?

Canada has ratified the 1990 convention, which sets out the rights of people under 18, but the U.S. is one of very few countries that has not ratified it.

Karim Khadr, brother of Omar Khadr, along with his sisters, in black, and mother, Maha Elsamnah (white scarf), takes a picture as they leave the Supreme Court of Canada hearing Omar's case in Ottawa on March 26, 2008. (Tom Hanson/Canadian Press)

It is widely expected that Khadr's lawyers could invoke legal obligations Canada has under the convention. However, Macklin is concerned that the government may flout its international statutory or constitutional legal obligations if "it's politically expedient to do so."

At the very beginning of this case, the government did express concern about Khadr's age. That soon changed.

Just before Khadr's transfer from Afghanistan to Guantanamo in 2002, Canadian officials were directed to "claw back on the fact that he is a minor."

Those instructions not to publicly raise the age issue came from Colleen Swords, the chief legal adviser at Foreign Affairs.

U.S. navy Capt. John Murphy, chief prosecutor for the military commissions, speaks to reporters after the sentencing of Khadr at his military trial at Guantanamo Bay on Oct. 31, 2010. (Colin Perkel/Canadian Press)

In an interview Nov. 1, 2010, on CBC Radio's As it Happens, the chief prosecutor at Guantanamo, Capt. John Murphy, told Carol Off that Khadr's age and his upbringing were already mitigating factors in determining his sentence.

How soon could Khadr get parole?

In Canada, an offender is usually eligible to apply for parole after serving one-third of a sentence. A prisoner can apply for day parole six months before full parole.

Under Canadian law, Khadr will be eligible for a parole hearing in July, 2013, at which point he will have served one-third of his sentence.

Unlike the U.S. military commissions, under Canada's International Transfer of Offenders Act any time spent in custody between arrest and sentencing counts as time served.

Because the act also says that an offender is eligible to apply for parole after "five years, if they were 14 or 15 years old at the time the offence was committed," Khadr may be applying for parole his first day back in Canada.

(Even if Khadr were eligible before his transfer, it would not matter. Under those circumstances, the act stipulates that "the day of their transfer is deemed to be their day of eligibility.")

Ottawa lawyer Paul Champ, who has handled a number of prisoner transfers, argues it would not matter in determining Khadr's equivalent Canadian sentence whether he is considered a child or an adult.

Lawyer Paul Champ speaks to reporters during a break at a hearing in Gatineau, Que., in October 2009. (Sean Kilpatrick/Canadian Press)

Prior to sentencing Khadr was in custody for more than eight years and Champ says "Canadian law would treat that as 24 years, because you get triple time for pre-sentencing custody."

Champ says that by the time Khadr returns, "for the purposes of Canadian law, he has already served 25 years" and therefore eligible to apply for parole immediately.

However, the Transfer Act states "the National Parole Board is not required to review the case of a Canadian offender until six months after the day of their transfer."

What will determine whether Khadr's parole application is successful?

Khadr will be eligible to apply for parole, but that does not mean it will be granted.

The Parole Board of Canada will look at well-established criteria in reaching a decision. All aspects of the case and the individual are considered, including the release plan, the likelihood of recidivism and, especially, the risk to society.

If the board believed Khadr would join a terrorist group, for example, it is hard to imagine he would go anywhere until he has served the full sentence.

Release opponents could make a case similar to what the prosecution presented at Khadr's sentencing hearing. Khadr's side could present evidence that he was tortured, coerced and abused, in order to argue that the plea agreement was signed under duress, and that his family made him become a child soldier.

The government could intervene in opposition to Khadr's parole application, but Harris expects it will "stay as far as possible away from this situation" unless there is a contrary agreement.

Accepting responsibility for a crime is normally an important sign that a convict is ready for parole. Macklin said the parole board will need "to rethink that in the context of this conviction."

Khadr is shown in an interrogation room at the Guantanamo Base military prison while being questioned by CSIS. This image was taken from a 2003 surveillance video and released by his Canadian lawyers in 2008. (Canadian Press)

How might Canada's security agencies respond to Khadr's release?

Harris told CBC News that it is "difficult for me to imagine conditions under which he would be free of intimate security-intelligence interest in his doings."

Harris expects a great deal of tax revenue will be expended shadowing Khadr, but he is more concerned that a possible Khadr court victory against the government could weaken morale in Canada's security and intelligence bodies.

"We don't want our defenders to be so reticent that we would find ourselves unnecessarily exposed to the depredations of extremists."

What is the historic importance of the Khadr case?

One of the challenges ahead for lawyers and judges in this case is that there has been very little prior jurisprudence that is directly relevant, meaning they have few precedents to work with in the Khadr case.

Canadians were evenly split in their opinions on whether Khadr should or shouldn't be allowed to serve even part of his sentence in Canada in an Ipsos poll conducted around the time Khadr was being sentenced. (Whether respondents thought Khadr should spend any or all of his time where he's now locked away — Cuba — is unknown. Instead the poll asked them about the U.S., a country the plea agreement bans Khadr from entering.)

And more than two-thirds of the adult Canadians polled told Ipsos that in their view, "Khadr probably is guilty and this plea bargain is too generous."

But for Audrey Macklin: "This will be a case that in a few years people will look back on in shame."

Macklin attended hearings in Guantanamo as an observer for Human Rights Watch.

"We will tell a story about how it was a different time, how 9/11 cast a long shadow, we were in the midst of a moral panic about terrorism; in combination with Omar Khadr's family — his father, his mother, his sister — the things they had done and said," she added.

Macklin has been involved with the Khadr case for five years and maintains a website archiving legal documents about the case. She expects that eventually "we will distance ourselves from it, and we will pretend that the past is another country."

What happens if his appeal is successful?

According to Sam Morison, named Khadr's lawyer by the U.S. Office of the Chief Defense Counsel, Khadr's legal team believes that "none of the charges" to which he pleaded guilty are war crimes under international law.

"If we are correct about that then the convictions are invalid and would have to be vacated," Morison said.

If Khadr is successful in his appeal, the Canadian government would have to release him from jail immediately.

"There would be no basis for Canada, for the Canadian government, to take a position on this one way or the other," Morison said.

"Under the provisions of an international transfer agreement, the receiving state … takes responsibility for executing the judgment. But they have no role in determining the validity of the underlying conviction. That's a matter for the U.S. courts," Morison said.

"If the U.S. courts were to throw out Khadr's convictions, there would no longer be any legal basis to hold him in prison."

With files from The Canadian Press