Common Law Police Powers and the Rule of Law

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Rule of Law, Police Powers, Ancillary Powers, Critique, Retroactive Approval, Predictability in Law


Common law police powers have long been a source of some dispute in the Canadian criminal justice system. On the one hand, their existence is difficult to reconcile with predictability in the law, since in any individual case where a new power is created (generally referred to as use of the "ancillary powers doctrine"), it would not have been possible to know in advance that the police were actually acting legally. On the other hand the benefit for society purchased with that ambiguity is a more tailored response to the particular problem, which might also lead to better results in future cases. One can reasonably fall into a variety of places on the scale defined by the values of predictability and protection of society.

Recently, however, two trends can be observed in the use of common law police powers. Where at one point they were a rarity, and perhaps only served as a safety valve, more frequently today courts seems to regard the use of the ancillary powers doctrine as one of the tools always brought to the table. That trend reflects a movement toward the tailoring end and away from the predictability end of the spectrum.

The second trend is more worrying. This trend reflects not merely a greater willingness to tailor the law for particular fact patterns, but a change in exactly what it means for the police to have a common law police power. In essence, the Supreme Court seems to have begun to interpret the ancillary powers doctrine in a way which ceases to think of the police as having actual "powers" at all, but rather as whether we should retroactively approve or disapprove of the decision made on the spot by the individual officer. If a court approves, the power existed: if a court did not approve, the power did not exist. Ultimately that approach would challenge foundational notions of our criminal justice system, because it will amount to rule by people, not by law.