Riots bean almost a week ahead of the G-20 summit meeting in Toronto in 2010 (Mark Wallis/Wikimedia Commons)

While Canadian authorities were aware of the operation, it still is rare for allies to give each other permission to run spying operations in their own countries.

The documents reportedly do not reveal the targets of the NSA's spying, but does describe the NSA's instructions at the summit as "providing support to policymakers". Most of the G20 document leaked by Snowden was devoted to details relevant to security at the summit.

Additionally, the CBC story quoted the leaked document as saying that there was no information that the Al-Qa'ida or other Islamic extremists would target the event, but instead said that a more likely security threat would come from "issue-based extremists". This turned out to be true, with protests of as many as 10,000 people resulting in a number of arrests by twice as many policemen in Toronto.

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