It’s long been evident to Western security services that professional jihadists view Canada as a safe staging base for operations elsewhere, a place to raise funds and organize plots to be executed outside Canada. Hence terrorism conducted in that country is considered “off message” and counterproductive, which explains the dearth of mass-casualty jihadist terrorism in Canada, despite the large numbers of radicals there.

For Al-Qa’ida and the Islamic State, Canada is especially attractive because it’s so close to the United States. Jihadists are well aware that Canada takes in large numbers of refugees, and Ottawa’s benefits are generous. Moreover, newcomers can get a coveted Canadian passport rather quickly, which enables easy travel all over the world. With a Canadian passport in hand, access to America is no problem, since U.S. border enforcement isn’t eager to detain Canadians without reasonable cause, since we don’t want Canadian authorities doing the same to Americans.

None of this is new. CSIS is supposed to screen refugees for security issues but, as everywhere, that task is exceptionally difficult, no matter what politicians tell you. The warning shot that wasn’t seriously heeded was Al-Qa’ida’s Millennium Plot at the end of 1999. This involved Algerian jihadists based in Montreal, and controlled out of Bosnia, that aimed to blow up Los Angeles International Airport.