International standards recognize that children under the age of 18 are a particularly vulnerable group, and are entitled to special care and protection because they are still developing physically, mentally and emotionally. These standards include certain key principles, including the use of detention only as a measure of last resort, the separation of children from adults, the right of children to maintain contact with their families, and the right to a prompt determination of their case.
In addition, treaties binding on the United States recognize the special situation of children who have been recruited or used in armed conflict, and their rights to prompt demobilization, and rehabilitation and reintegration assistance.
In cases where children are believed to have committed war crimes, they can be formally charged and should be provided with counsel and tried in accordance with international standards of juvenile justice.
Here's more on Omar's capture and his dysfunctional family life, including details about how a bullet blinded him in one eye during the gunfight.
As Jeanne D'Arc of the now defunct Body and Soul blog said at the time,
Omar Khadr is as much a victim of these people as a member of the family. He's eighteen years old. When he was captured in Afghanistan, he was fifteen -- a child turned into a soldier by parents from hell. And our government's response to this victim of child abuse was to abuse him further.
More on the Khadr family is here.
And yes, there are reports he was tortured. In 2005, The Toronto Star reported,
In February, his U.S. lawyer told reporters the teenager had been used as a human mop to clean urine on the floor and had been beaten, threatened with rape and tied up for hours in painful positions at Guantanamo Bay.
In 2006, Rolling Stone had this feature article, The Unending Torture of Omar Khadr.
Omar should be sent back to Canada for rehabilitation. Or trial by the juvenile justice system. He should not be facing murder trial by tribunal in Guantanamo.