The Conservative government is vowing to move quickly on two fronts to strengthen the powers of Canada's spy agency and police forces in the wake of the killings of two soldiers this week – including a contentious measure to alter the threshold for preventative arrest.

New legislation giving the Canadian Security Intelligence Service (CSIS) the ability to better hide the identities of its informants and allow Canada to share more intelligence information with its allies is to be tabled in the House of Commons as early as Monday or Tuesday, according to a senior government source.

In addition, Justice Minister Peter MacKay told The Globe and Mail on Friday that, in co-operation with other departments and agencies, he is "exploring a broad array of options, including legislative and preventative" to help better protect Canadians.

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Measures now under consideration include changing the so-called threshold for preventative arrests and more closely tracking and monitoring people who may pose a threat, such as requiring them to check in with an officer regularly even without any charges against them. Being looked at, too, is potential legislation that would make it a crime to support terrorists' acts online, says a senior government source.

Mr. MacKay wrote in an e-mail that new measures "will build on our record of better equipping our security forces and law enforcement with the critical tools they need to intercept and disrupt threats and ultimately convict and incarcerate those who pose a danger to Canadian families and communities."

The government source cautioned that legislation has not yet been written. But he pointed out that Prime Minister Stephen Harper indicated in his address to the Commons Thursday – the day after the gunfight in the Centre Block and the shooting of Corporal Nathan Cirillo at the National War Memorial – that police powers and laws need to be strengthened in the "area of surveillance, detention and arrest." Mr. Harper vowed that the work that is under way will be "expedited." He has repeatedly referred to the two killings as acts of terrorism.

Opposition parties, however, are refusing to go that far. Instead, NDP public safety critic Randall Garrison said Friday that his party is waiting for the police to finish its investigations in the Quebec and Ottawa incidents before it draws any conclusions. As for trading freedoms for more security, Mr. Garrison said his party does not believe there is any "contradiction between civil liberties and public safety … it's not a tradeoff between the two."

Security expert Wesley Wark also preached caution: "Let's be sure we know everything that was done and everything that was missed before we come up with fixes."

Mr. Wark said that he "would be very cautious about deciding that the real fix is in extending legal powers or the real fix is in let's go and use those preventive arrest measures … I would hesitate to advocate for that until we know what really went wrong."

Mr. MacKay, meanwhile, told reporters earlier this week, after a soldier was run down by a car near Montreal and killed, that the changes being considered relate in part to the use of powers under Section 810 of the Criminal Code to place restrictions on individuals – such as those that help officials monitor them – without actually laying a charge. Section 810 includes a specific, rarely used power to place terror suspects under a kind of peace bond. Had similar changes been in place before Monday's attack, the Crown could have "put certain provisions and supervisory requirements on an individual," Mr. MacKay said.

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Whether the changes might also include the creation of new criminal offences or granting of other police powers is unclear. Mr. MacKay said his review was focusing more on increased monitoring powers, not increased arrest powers, but also said government is "examining any and all measures that will increase public safety in this regard."

Police support a review or enhancement of the measures.

RCMP Commissioner Bob Paulson told reporters Thursday that "we need to look at all options in terms of trying to deal with this sort of difficult and hard-to-understand threat …" He said there has to be a balance between allowing police to "act decisively, quickly, preventatively and perhaps at a threshold that is somewhat lower" – and not "throwing someone in jail forever …"

Ottawa Chief Charles Bordeleau agreed: "I think we're seeing a gap evolve in law enforcement's ability to maintain control over these individuals that are being radicalized." He said he thinks there's an opportunity to review existing laws "to provide us the tools within the Constitution that allow us better monitoring mechanisms, opportunities to prevent these types of incidents from taking place and to keep our communities safe."

With a report from Kathyrn Blaze Carlson