For example, where the decision-maker is considering a discretionary matter that is based primarily on factual and policy matters having very little legal content, the range of possible, acceptable outcomes open to the decision-maker can be expected to be quite broad. As a practical matter, the breadth of the range in that sort of case means that it will be relatively difficult for a party applying for judicial review of the decision to show that it falls outside of the range. In other cases, however, the situation might be different. For example, where the decision-maker is considering a discretionary matter that has greater legal content, the range of possible, acceptable outcomes open to the decision-maker might be narrower. Legal matters, as opposed to factual or policy matters, admit of fewer possible, acceptable outcomes.
On the facts (a review of the decision of a Minister's delegate in a taxation matter):
These observations echo those of Justice Binnie in his last set of administrative law reasons (see paras. 85-87). This foregoing analysis suggests that although the reasonableness standard applies in this case, the legal aspects involved in the Delegate’s decision tend to narrow the range of possible, acceptable outcomes. If, for example, the Delegate were to take an unacceptable view of the legalities, that might take her discretion outside of the range of possible, acceptable outcomes and render it unreasonable.
Justice Stratas goes a little bit further. His suggestion that the range of possible outcomes is naturally narrower where a decision contains some legal components is novel, I think.
I am skeptical of this approach, as I have explained here and here, but Justice Stratas has -- as usual -- done a fine job of explaining complicated concepts in clear and coherent terms.