Discretion'Discretion' in the legal sense refers to a delegated authority to make a decision as one thinks fit, usually on the part of a public authority.
. MDS Inc. v. Factory Mutual Insurance Company
In MDS Inc. v. Factory Mutual Insurance Company (Ont CA, 2021) the Court of Appeal considered the standard of review that applies to an award of prejudgment interest (which it held to be discretionary):
The standard of review for the award of prejudgment interest. Meekis v. Ontario
 The trial judge awarded prejudgment interest at MDS’ actual cost of borrowing, including compound interest, under ss. 128 and 130 of the Courts of Justice Act, R.S.O. 1990, c. C.43 (“CJA”).
 Provided that the exclusions to an award of interest set out in the CJA do not apply, the trial judge’s decision to award prejudgment interest at a rate higher or lower than provided for in ss. 128 and 129 is discretionary: see Tribute (Springwater) Limited v. Atif, 2021 ONCA 463, at paras. 26-27. In exercising discretion to award interest at a rate higher or lower than provided for in ss. 128 and 129, the trial judge must take into account changes in market interest rates, the circumstances of the case, the amount claimed and recovered, and other relevant considerations: CJA, s. 130(2).
 As this court held in Krieser v. Garber, 2020 ONCA 699, 70 C.C.L.T. (4th) 40, at para. 46:
The court will only interfere with the exercise of discretion if it was based on an error of law (determined on a correctness standard), a palpable and overriding error of fact, the consideration of irrelevant factors or the omission of factors that ought to have been considered, or if the decision was unreasonable in the sense that it is not compatible with the judicial exercise of discretion. [Citations omitted.]In particular, the trial judge must consider the factors set out under s. 130(2) of the CJA.
 As such, the standard of review in respect of this issue is that of error of law or palpable and overriding error.
In Meekis v. Ontario (Ont CA, 2021) the Court of Appeal considered the improper exercise of discretion:
 The appellants’ core misfeasance allegation on the unlawful act element is that the respondent coroners exercised their discretion to knowingly discriminate against a class of persons which included the appellants. In my view, this may be understood as an exercise of discretion for an improper purpose. Discretion must be exercised reasonably and, as indicated, it cannot be exercised based on discriminatory considerations. Rather, it should be structured by the relevant statutory factors under the applicable legislative scheme: see, Ojeikere v. Ojeikere, 2018 ONCA 372, 140 O.R. (3d) 561, at para. 63.. Connor Homes v. Director
In Connor Homes v. Director (Div Ct, 2021) the Divisional Court considered deference accorded discretionary decision on appeal:
Deference on Discretionary Decisions. Bell Canada v. British Columbia Broadband Association
 Deference is owed at both stages of the Mohan/White Burgess analysis. At the first step of determining whether the proposed evidence meets the threshold admissibility requirements (here necessity and the application of the LAT gatekeeping role), appellate interference is justified only where the finding is “clearly unreasonable, contaminated by an error in principle, or reflective of a material misapprehension of evidence.”
 At the second step, discretionary gatekeeping, the decision maker must determine whether the benefits of admitting the evidence outweigh the “consumption of time, prejudice and confusion”. The Court of Appeal has stated that this balancing is “equally case-specific” and “involves the exercise of judicial discretion, not the application of a bright line rule.” The determination at the gatekeeper stage is entitled to deference “absent an error of law or of principle, or a material misapprehension of the evidence.”
 The Supreme Court of Canada set out the standard of review for reversing a judge’s exercise of discretion in Penner v. Niagara (Regional Police Services Board) at paragraph 27:
A discretionary decision of a lower court will be reversible where that court misdirected itself or came to a decision that is so clearly wrong that it amounts to an injustice: Elsom v. Elsom, 1989 CanLII 100 (SCC),  1 S.C.R. 1367, at p. 1375. Reversing a lower court’s discretionary decision is also appropriate where the lower court gives no or insufficient weight to relevant considerations: Friends of the Oldman River Society v. Canada (Minister of Transport), 1992 CanLII 110 (SCC),  1 S.C.R. 3, at pp. 76-77.
In Bell Canada v. British Columbia Broadband Association (Fed CA, 2020) the Federal Court of Appeal considered one indicia of fettering discretion:
 ... An administrative decision-maker fetters the exercise of their discretion by relying exclusively on an administrative policy without regard to the law (Stemijon Investments Limited v. Canada (Attorney General), 2011 FCA 299, 475 N.R. 341, at paragraphs 24 and 60).. Ontario (Labour) v. Cobra Float Service Inc.
In Ontario (Labour) v. Cobra Float Service Inc. (Ont CA, 2020) the Court of Appeal sets out the standard of review for discretionary decisions:
 Discretionary decisions attract a high level of deference on appeal. Appellate courts will only intervene where there is a clearly identifiable legal error, a material misapprehension of the relevant evidence, or a result that is clearly wrong in the sense that it is not defensible on the relevant law and facts: Popack v. Lipszyc, 2016 ONCA 135, 129 O.R. (3d) 321, at para. 25. . CNH Canada Ltd. v. Chesterman Farm Equipment Ltd.
In CNH Canada Ltd. v. Chesterman Farm Equipment Ltd. (Ont CA, 2018) the court states the obvious point that a legally delegated discretion must be exercised in accordance with the law:
 As explained above, an appeal from a Tribunal decision under s. 5 of the Farm Implements Act is limited to questions of law. As with all discretionary decisions, the Tribunal’s discretion to award costs must be exercised in accordance with the law: see generally, Baker v. Canada (Minister of Citizenship and Immigration), 1999 CanLII 699 (SCC),  2 S.C.R. 817, at paras. 53, 56; John Doe v. Ontario (Finance), 2014 SCC 36 (CanLII),  2 S.C.R. 3, at para. 52. If the Tribunal makes an error in principle or the award is clearly wrong, appellate intervention may be warranted: see Hamilton v. Open Window Bakery Ltd., 2004 SCC 9 (CanLII),  1 S.C.R. 303, at para. 27; Kerry (Canada) Inc. v. DCA Employees Pension Committee, 2007 ONCA 416 (CanLII), at paras. 170-71, aff’d Nolan v. Kerry (Canada) Inc., 2009 SCC 39 (CanLII),  2 S.C.R. 678.