The authority to seal off parts of Toronto for the G20/G8: Knowlton v. R., [1974] S.C.R. 443

This passage may allow limiting access to a small area -- it surely cannot allow major parts of Toronto to be sealed off from the public. Also, note this decision predates that Charter.

"It is notorious and of common knowledge that the official visit of the head of state or high rank dignitary of a foreign country, friendly as either may be, is an event that frequently engenders a real or apprehended threat to the preservation of peace and that calls, therefore, for the adoption of proper and reasonable security measures in and by the host country. Demonstration of this assertion can hardly be here more to the point than by merely referring to the criminal assault actually committed on the person of Premier Kosygin, in the City of Ottawa, a few days only before his visit to the City of Edmonton. This assault was instantly publicized throughout Canada and was, indeed, while being committed, witnessed on television by a very great number of persons in the country including, admittedly, the appellant himself. From these facts, it is only natural to draw the inference that Canadian officials specially involved in the preservation and maintenance of peace, order, public safety and of the security of our visiting dignitary, gained immediate knowledge of this event of regrettable import.

According to the principles which, for the preservation of peace and prevention of crime, underlie the provisions of s. 30, amongst others, of the Criminal Code, these official authorities were not only entitled but in duty bound, as peace officers, to prevent a renewal of a like criminal assault on the person of Premier Kosygin during his official visit in Canada. In this respect, they had a specific and binding obligation to take proper and reasonable steps. The restriction of the right of free access of the public to public streets, at the strategic point mentioned above, was one of the steps—not an unusual one—which police authorities considered and adopted as necessary for the attainment of the purpose aforesaid. In my opinion, such conduct of the police was clearly falling within the general scope of the duties imposed upon them. "