CSIS has little power under its current mandate to prevent recruitment by radical groups such as ISIS, hampering its battle to root out homegrown terrorism, security experts say.

“It’s not illegal to leave the country,” said MacEwan University professor Jean Christophe Boucher. “It’s not illegal to pay somebody else's plane ticket, it's not illegal under certain conditions to convince somebody to go abroad.”

This week CBC News revealed several cases of Canadian women believed to have  joined ISIS,

In a case linked to Edmonton, a woman said she’s furious her Canadian sister left last summer for the Islamic State, even while she was under the watch of CSIS.

“I don't understand why they didn't stop her at the airport in Toronto. She told me in a conversation that they followed her all along every step of the trip,” she said.

She also questioned why the agency didn’t tell her family what they knew, so they couldtry to stop her, and why no steps were taken to arrest or detain the Edmonton woman believed to have radicalized the young woman and paid for her plane ticket.

“I would like her to be locked up, so that she can't cause any more families to go through what I’m going through with my family.”

CSIS: 'No mandate to intervene'

CSIS won’t comment on specific investigations. But in a statement, the agency said it can only collect and analyze information and doesn’t have the "mandate to intervene to prevent terror plots from developing.”

Experts agree, pointing that out CSIS was set up following the 1981 landmark McDonald inquiry into “troubling activities by the RCMP," which recommended separating criminal and security intelligence.

“CSIS has no powers to disrupt,” said Christian Leuprecht, associate dean with the Royal Military College of Canada. “CSIS would only be able to share (intelligence) with police if there were sufficient grounds to launch a national security investigation.”

RCMP would then have to start their own investigation, he said.

Boucher points out that as long as people don’t encourage others to do something illegal, their rights are protected by the charter.

“There is a sufficiently strong and high threshold on how and when you can detain people on suspicion.

“Some people have weird ideas but we don't arrest them and we don't block them from going abroad. And here, I think, CSIS’s room to manoeuvre was really constrained by the kind of laws that apply to every Canadian.

"And as long as you don’t do anything illegal, then CSIS, nor the RCMP, nor local police, have any capacity to actually arrest and detain you. In this case, it’s clear the young woman did nothing specifically illegal, except wanting to join that group.”

Prohibited from sharing intelligence

Leuprecht said CSIS is prohibited from sharing intelligence with anyone not immediately involved in the investigation.

“Hence, CSIS is prevented from actually talking to the parents about what they believe they might be observing,” he said.

He said Bill C-51, the Conservative government’s proposed anti-terrorism legislation, would vastly expand the agency’s powers in a case such as this one.

Among the new capabilities, under the proposed legislation it would be easier to share data among agencies, cancel a plane ticket, stop someone from boarding a plane, intervene financially, or obtain information from telecommunications companies, said Leuprecht.

Restrictions on suspects, such as who they communicate with or their Internet use, could also be imposed more easily, and the advocacy and the promotion of terrorism would be an offence, he said.  

The NDP and other critics have said Bill C-51 lacks sufficient oversight mechanisms, but Prime Minister Stephen Harper insists the proper checks and balances are in place.

Calgary Imam Abdi Hersy, who has been urging young Muslims not to join ISIS, warned the legislation will further alienate some Muslim youth and make his job even harder.

Some disaffected young people may actually be more motivated to leave the country if Bill C-51 is enacted, he said.

Hersy and the federal opposition say the government needs to focus on prevention long before youth become radicalized.