Two deadly attacks perpetrated against Canadian soldiers by suspected extremists are raising the stakes in the domestic fight against terrorism.

In recent months, the public and politicians have pushed federal security officials to get more aggressive. One response has been renewed efforts to block or revoke passports to stop the exodus of extremists to fight with the Islamic State jihadis and related groups.

Yet counterterrorism officials increasingly regard extremists in Canada as more menacing and harder to predict. Security measures are already stretching to their legal limits – yet Parliament is set to confer more powers to federal agents as the threats continue to mount.

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"This will lead us to strengthen our resolve and redouble our efforts," Prime Minister Stephen Harper said Wednesday evening in a televised address. He said that the violence in Ottawa and near Montreal will lead his government to beef up counter-terrorism efforts.

Public Safety Minister Steven Blaney highlighted one such package last week – the looming legislative amendments for the Canadian Security Intelligence Service. The minister has said this bill would seek to better safeguard informants' identities and allow Canada to share information with U.S. and British counterparts.

That might just be the start.

The Globe and Mail has learned that Ottawa officials are also talking about whether to give CSIS explicit legislative permission to engage in "threat-diminishment" – a power that the spy agency's watchdog recently pointed out that CSIS uses, but the law doesn't explicitly permit.

If such a measure were to receive parliamentary approval, CSIS intelligence officers would have greater leeway to deal with their targets.

Right now, some intelligence-gathering techniques – such as CSIS officers aggressively interviewing a young radical's parents, or his bosses – are in a legal grey area. Such methods risk wrongly red-flagging individuals as potential terrorists to parents or peers when they haven't been charged.

Critics of the spy agency have pointed out that any sort of longer leash for CSIS could set it on a path that got its predecessor in trouble. In the 1980s, the RCMP Security Service was disbanded after it was caught committing crimes – such as burning barns to prevent Quebec separatist extremists from congregating with other radical groups.

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Yet these days, by the standards of the Canada's closest allies, federal agents can seem shackled.

In Britain, the Home Secretary has already announced she will be seeking "Extremist Disruption Orders" – a new legal power to muzzle suspected extremists and prevent them from speaking out in public or on the Internet.

Similar "foreign fighter" legislation now being contemplated in Australia has led Human Rights Watch to complain this week that this package "risks criminalizing free speech" and preventing citizens' legitimate travel to war zones.

The shared concern among officials in several countries is that they are overwhelmed by the domestic implications of the threat represented by Islamic State's so-called caliphate in Syria and Iraq.

Officials say the territory has created a jihadi nexus that similar groups, such as al-Qaeda, never had. This has increased the tempo of the work of monitoring extremists – and keeping tabs on travellers, sympathizers or jihadis returning from war zones is becoming more time-and-money consuming.

This is because 24-hour eyes-on surveillance of any suspect can involve at least a dozen undercover officers and a half-dozen cars.

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Monitoring phone conversations is similarly intensive – under Canada's laws, this cannot be automated. Live operators have to listen to wiretaps.

And, as always, police need evidence of provable crimes to put anyone in jail.