The court ruled that the board made mistakes when it turned down Joshua Key's claim for asylum.

Mr Key served in Iraq in 2003 before deserting to Canada with his family while on leave in the US.

The ruling could affect scores of other US soldiers sheltering in Canada who have refused to fight in Iraq.

Possible deportations

Joshua Key served in Iraq as a US combat engineer in Iraq in 2003.

He claims that he witnessed several cases of abusive acts against civilians and the killing of innocent people.

While on leave at home in Oklahoma, he decided that he would not return to duty and took his family to Canada where he applied for asylum.

Although the Canadian refugee board found Mr Key credible, it rejected his application, saying that unless his claims of abuse constituted a war crime, they did not justify his desertion from the US army.

In its ruling, the federal court has disagreed with that analysis, saying that being forced to participate in military misconduct, even if it stops short of a war crime, may support a claim to protection in Canada.

There are at least 200 American war deserters in Canada and many face deportation after their asylum cases were also rejected.

Joshua Key's lawyer said that the ruling may help their cases.

The Canadian government is reviewing the court's decision and has not said whether it will appeal.

BBC