The topic of 'discretion' is quite broad but basically it refers to a delegated authority to make a decision as the delegatee thinks fit - be it a judge, an adjudicator or some other form of public authority. The most common 'discretion' issue these days is the review (appeal-JR) 'standard of review' (SOR), where the court decides how much deference to give to discretionary decisions on appeal or judicial review.
IMHO a live legal issue is that: 'discretion may only be exercised consistent with the law'. I think that the Okanagan case reads the 'law' under this doctrine very broadly - to typical day-to-day judicial adjudication rather than only statutory law - which in term would limit the range of a decision-maker's discretion.
