The rules of engagement governing the Canadian military do not prevent it from targeting and killing ISIS fighters holding Canadian passports, according to military experts and the Department of National Defence.

But one constitutional expert believes the Charter of Rights and Freedoms protects Canadian enemy combatants from being specifically targeted by the military, with some exceptions.

As ISIS's defeats on the battlefield in Iraq and Syria continue to mount, and jihadi fighters who ran off to join the terrorist organization begin returning home, the challenge of how to deal with them has seized many Western governments.

Several of Canada's allies have a policy of directly targeting militants for death on the battlefield to prevent them from coming home. But the Trudeau government has not followed the example set by Britain, France and the United States.

In Canada, at the end of 2015, the government said it was aware of about 180 so-called terrorist travellers — individuals who had travelled overseas to join terrorist groups — and of another 60 who had returned to Canada.

"Canada does not engage in death squads," Public Safety Minister Ralph Goodale told CBC News Network's Power & Politics recently.

Byrne Furlong of Defence Minister Harjit Sajjan's office clarified: "Enemy combatants are treated in accordance with the Law of Armed Conflict. This is regardless of their country of origin. No directive to eliminate foreign fighters has been given to Canadian Armed Forces personnel."

The Law of Armed Conflict at the Operational and Tactical Levels, which lays out the international rules of engagement for Canadian soldiers, says:

"Unlawful combatants are legitimate targets for such time as they take a direct part in hostilities. Civilians who take a direct part in hostilities (other than a levée en masse) are unlawful combatants. They lose their protection as civilians and become legitimate targets."

Stuart Hendin, a lawyer and instructor at the Royal Military College and Canadian Forces College, said, "It doesn't matter whether the individual is a Canadian or not, so long as that individual is part of [ISIS], which is an organized structure, and is engaged in a conflict, that individual may be a legitimate target."

Hendin also said the use of drones, the method employed by some of Canada's allies for the targeted killing of jihadis, is not a legal obstacle, noting: "A drone is simply another type of weapon platform."

Speaking on background, one senior DND official told CBC News that drone strikes "are not just speculation. We are part of a coalition that has these capabilities."

Public Safety Minister Ralph Goodale responds to Conservatives who accuse him of spending money on terrorists rather than veterans. 1:23

Charter concerns?

Although the government of Canada cited the binding, international Law of Armed Conflict, that is not the only law it must follow. One well-known constitutional lawyer believes the Charter of Rights and Freedoms could still stand in the way of a campaign to ensure jihadis with Canadian passports don't come back.

That's because, while killing Canadian terrorists incidentally in the course of a war on Islamic State is lawful, drawing up a list of Canadians to kill may not be.

"I think that if the Canadian state engages in the targeted killing of a Canadian citizen without any other due process, then that would appear to violate the person's right to life under the Canadian Charter," said Carissima Mathen, who teaches constitutional law at the University of Ottawa.

Section 7 of the Charter guarantees "the right to life, liberty and security of the person and the right not to be deprived thereof except in accordance with the principles of fundamental justice."

A member of the Kurdish security force shows a reporter the inside of an ISIS fighter's house in February in Bashiqa, Iraq. The town in the Mosul district was liberated last November after being under ISIS control for two years. (Ryan Remiorz/Canadian Press)

The right is not absolute, said Mathen, noting that Canada can imprison criminals without violating Section 7's promise of liberty, and police can kill an armed suspect without violating the right to life.

"If we're talking about Canada taking an action that happens to kill Canadian citizens, that's very different than it developing a policy that has not been authorized by Parliament, not been authorized by law, where they're selectively targeting people for execution," she said.

There are exceptions, Mathen noted, where the government "could point to extreme or exigent circumstances in which it was forced to act" if, for example, there was a need to halt a specific plot or threat.

'Death Squads'

The term "death squad" originated in Latin America and was used to describe clandestine groups organized by right-wing governments, some of them military dictatorships, to abduct and murder political opponents at home.

Any campaign to kill Canadian members of ISIS would be undertaken by the Canadian military and its coalition partners, operating in a foreign country that is in a state of war.

The fact of the matter is, these people are mobile. - Public Safety Minister Ralph Goodale

Canadian allies such as the U.S., the United Kingdom and France have all made deliberate efforts to kill jihadis holding citizenship from those nations. Canada remains in the anti-ISIS coalition alongside them and hasn't denounced them for running "death squads."

Still, Goodale makes it clear Canada prefers to lay charges rather than go after targets on enemy soil.

"Wherever the evidence is available to lay a charge, the charges are pursued," he said Friday.

Canada has only been able to bring charges against two of an estimated 60 jihadi returnees, and four in absentia prosecutions against the nearly 200 jihadis who are still believed to be abroad.

John Maguire, a Canadian, appeared in ISIS propaganda videos. He was reportedly killed fighting for ISIS in Syria. (Trial evidence)

In some cases, Goodale said, the intelligence gathered on Canadian fighters is not up to the evidentiary standards required in a Canadian court. In others, the government foregoes prosecution to protect confidential sources.

"The defence counsel will want to examine the source of that evidence," Goodale said. "That's our adversarial legal system. One side says this, the other side gets to question what is the origin of what you're alleging. If the origin is confidential information from a source that's in the midst of a terrorist operation or activity, if you disclose the identity of your source, that person is likely dead."

Goodale insisted Canada is using "all lawful tools" to stop Canadian terrorists.

"We certainly don't encourage them to return," Goodale said on Friday. "But the fact of the matter is, these people are mobile."