Justice LeBel affirmed in MacDonald, at para. 26, that where the conduct of the police goes beyond that which is permitted by the implied license to knock, the conditions of that licence have been breached and the person carrying out the unauthorized activity approaches
the dwelling as an intruder.
On the other hand, where the
intruder may pose a danger to the inhabitants of a
dwelling, the privilege of using such a device to repel has been recognized by most authorities, and the mere setting thereof in the
dwelling has not been held to create liability for an injury
as a matter of law.