Canada's spy agency will be granted the authority to intervene and disrupt threats to national security in a massive expansion of its powers as the federal government tries to make it easier to thwart terror plots at home and abroad, sources say.

The Canadian Security Intelligence Service's role is currently restricted to collecting intelligence, analyzing and reporting on dangers to Canada, but new anti-terror legislation to be unveiled Friday is expected to rewrite its mandate to allow CSIS agents to take action to foil security threats.

The new role for CSIS is one of a series of measures in the legislation promised after deadly attacks on Canadian soldiers last October that also saw a gunman storm Parliament Hill.

Story continues below advertisement

Ottawa is building in judicial oversight for this new CSIS power, however, and will require the agency to obtain a court warrant to flex its new muscles. As long as a judge approves, CSIS agents would be able to cancel someone's travel reservations, for instance, or disrupt a banking transaction or electronic communications.

The new power would lift a fundamental restriction on CSIS's activities and gives the agency a measure of authority that's currently reserved for police forces. CSIS, a civilian agency, was created in the early 1980s after an inquiry into the RCMP security service's illegal activities and civil-rights abuses recommended that policing be separated from intelligence gathering.

The Conservative government holds a majority of seats in the Commons and the legislation is expected to pass easily. The legislation is also expected to: criminalize the advocacy or promotion of terrorism; lower the threshold for preventative arrest or detention of suspected extremists; relax the requirements necessary to prevent suspected jihadis from boarding a plane; grant government departments explicit authority to share private information, including passport applications, or confidential commercial data, with law enforcement agencies; make it easier for authorities to track and monitor suspects.

Ottawa is also planning a more robust government-financed campaign to thwart radicalization in young people, separate from the legislation being unveiled Friday.

The government is expected to justify this new role for CSIS by saying that the agency is often the first in Canada to detect a threat because it's continually gathering intelligence and conducting surveillance, and is therefore best placed to act to disrupt a new threat before it can grow.

Today, CSIS informs the RCMP when it detects terror threats and hands the matter off, letting the Mounties conduct their own investigation. The Conservatives, however, will argue that Canada needs to be able to act more quickly in an environment where terrorist threats can rapidly escalate from concepts to planning to execution, sources say.

CSIS would still not be a law-enforcement agency after these legislative changes. It would not be granted authority to arrest or detain people, for instance.

Story continues below advertisement

Ottawa wants CSIS to be free, with a court's consent, to approach suspected jihadis, for instance, and confront them with all the details they've gained of their schemes, sources say.

Another example of how CSIS agents might use this new power is covertly disarming a bomb threat, sources say. If extremists planned to detonate trucks of explosives and CSIS was aware of this plot, agents would seek a judge's approval to intercept the explosives and render key ingredients inoperable so they could remove the threat but keep the scheme in place and continue to gather intelligence on the plotters.

The legislation is expected to be tabled around midday Friday, and Prime Minister Stephen Harper will address it from a community centre in Richmond Hill, Ont.

The Conservatives will go to great effort to make the case they've struck a balance between safeguarding the civil rights of Canadians and measures to enhance the country's security.

Legislation that criminalizes the promotion of terrorism, however, is a concern for legal experts who worry that Ottawa would curtail fundamental freedoms in the name of national security.

Mr. Harper has made it clear he sees a dire threat to Canada ahead in the wake of the murder of Canadian soldiers as well as deadly attacks on civilians in Australia and satirical cartoonists in France.

Story continues below advertisement

"The international jihadist movement has declared war," Mr. Harper said earlier this month. "They have declared war on any country like ourselves that values freedom, openness and tolerance. And we may not like this and wish it would go away, but it is not going to go away and the reality is we are going to have to confront it."