What is the current state of the law on undercover policing?

In the case of Kirzner v. The Queen, 1977 CanLII 38 (SCC), [1978] 2 S.C.R. 487 at 492-3, it is stated: ... Where "consensual" crimes are committed, involving willing persons, as is the case in prostitution, illegal gambling and drug offences, ordinary methods of detection will not generally do. The participants, be they deemed victims or not, do not usually complain or seek police aid; that is what they wish to avoid. The police, if they are to respond to the public disapprobation of such offences as reflected in existing law, must take some initiatives. They may, for example, use a spy, either a policeman or another person, to obtain information about a consensual offence by infiltration; they may make arrangements with informers who may be parties to offences on which they report to the police to enable the other parties to be apprehended; or the police may use decoys or themselves to act undercover to provide others with the opportunity to commit a consensual offence or to encourage its commission. Going one step farther, the police may use members of their force or other persons to instigate the commission of an offence, planning and designing it ab initio to ensnare others. The use of spies and informers is an inevitable requirement for detection of consensual crimes and of discouraging their commission; otherwise, it would be necessary to await a complaint by a "victim" or to try to apprehend offenders in flagrante delicto, an exercise not likely to be crowned with much success.