Judicial Review - SOR - The Role of Errors in 'Reasonableness'This is an interesting issue that was bound to occur sooner or later. While Vavilov's judicial review standard of review of 'reasonableness' makes no mention of 'errors' (ie. errors of law, mixed fact and law, or fact alone), rather leaving consideration of errors to appeals, errors can nonetheless be logically argued to be an aspect of 'reasonableness'. That's what happens here.
. Maritime Employers Association v. Syndicat des débardeurs (Canadian Union of Public Employees, Local 375)
In Maritime Employers Association v. Syndicat des débardeurs (Canadian Union of Public Employees, Local 375) (Fed CA, 2023) the Federal Court of Appeal considered the range of fact errors in a judicial review, in light of Vavilov's treatment of privative clauses:
 As held in Canada (Attorney General) v. Public Service Alliance of Canada, 2019 FCA 41, 432 D.L.R. (4th) 170, and Canada (Attorney General) v. Best Buy Canada Ltd., 2021 FCA 161,  F.C.J. No. 848 [Best Buy], in light of the development in administrative law over the past several years, paragraph 18.1(4)(d) of the Federal Courts Act, R.S.C. 1985, c. F-7 allows intervention in factual determinations even in the face of a privative clause such as section 22 of the Code.. Maritime Employers Association v. Syndicat des débardeurs (Canadian Union of Public Employees, Local 375)
 "However, the scope for intervention is very narrow. Paragraph 18.1(4)(d) of the Federal Courts Act provides that erroneous factual findings may provide the basis for intervention only if a decision was based on them and if they were "“… made in a perverse or capricious manner or without regard for the material before [the decision-maker]”". The statutory formulation of the test before the Federal Courts for unreasonable factual determinations is akin to what the Supreme Court said about the nature of unreasonable factual findings in Vavilov, where the majority noted at paragraph 126 that unreasonable factual determinations arise where the "“… decision maker has fundamentally misapprehended or failed to account for the evidence before it.”"" "
 A finding is perverse if it is made wilfully contrary to the evidence. Findings that are capricious or made without regard to the material before an administrative decision-maker include most notably circumstances where there is no evidence to rationally support a finding or where the decision maker failed to reasonably account at all for critical evidence that ran counter to its finding (Best Buy at para. 123).
 Here, none of the factual matters that the applicants raise rise to such a level. The applicants seek to have us instead set aside the CIRB’s findings and accept the conclusions advanced by their experts by calling on us to sift through all the evidence and reach a different conclusion. Indeed, they devoted the bulk of their written and oral arguments to a minute review of the evidence and urged this Court to re-evaluate it.
 We cannot do so. The CIRB was entitled to reject the conclusions advanced by the witnesses the MEA called for the reasons it gave. Contrary to what the applicants assert, the Board provided ample reasons for rejecting these conclusions, as the detailed review of the Board’s decision, set out above, demonstrates.
In Maritime Employers Association v. Syndicat des débardeurs (Canadian Union of Public Employees, Local 375) (Fed CA, 2023) the Federal Court of Appeal states that all types of error in a JR are subject to the same SOR of 'reasonableness':
 On the other hand, the CIRB’s factual findings and interpretation of the provisions in the Code are subject to review under the deferential reasonableness standard, as was held in at Watson at para. 16; Clark at paras. 8–9; and Grant v. Unifor, 2022 FCA 6, 340 A.C.W.S. (3d) 227 at para. 8. . BCE Inc. v. Québecor Média Inc.
In BCE Inc. v. Québecor Média Inc. (Fed CA, 2022) the Federal Court of Appeal considers 'errors' [ie. errors of law, mixed fact and law, and fact alone] as they feed into the JR standard of review (SOR) of 'reasonableness'. My experience in assessing reasonableness in this context has been that 'errors' per se are rather an element of appeal SOR, the JR SOR being assessed on a more 'global' perspective.
Here the court notes that errors alone, of whatever category, do not exhaust the factors that make a ruling unreasonable:
 It should be apparent that a tribunal can make an unreasonable decision without necessarily falling into one of the types of errors listed by the Supreme Court. The categories of unreasonableness are not closed. As a result, attempts to shoehorn alleged errors into Vavilov categories may be misguided, as they were here, and may simply obscure a more coherent explanation of the unreasonableness of a tribunal’s decision. To be sure, the Vavilov categories of error will, in many cases, provide a concise way of describing certain types of error but they do not form a mandatory template for identifying unreasonableness.. BCE Inc. v. Québecor Média Inc.
In BCE Inc. v. Québecor Média Inc. (Fed CA, 2022) the Federal Court of Appeal noted from Vavilov that errors in a tribunal's decision must be material before they can feed into the JR reasonability test:
 Turning now to Bell’s statement of issues, Bell’s memorandum of fact and law quotes extensively from the Supreme Court’s decision in Vavilov in which the Supreme Court continued its development of administrative law. In Vavilov, the Supreme Court identified certain kinds of errors which make a decision unreasonable, a teaching which Bell appears to have taken to heart.
 But it is not sufficient to simply point to errors in a tribunal’s reasons; the errors must be material to the outcome:
When resolving challenges to an administrative decision, courts must also consider the materiality of any alleged errors in the decision-maker’s reasoning. Under reasonableness review, an error is not necessarily sufficient to justify quashing a decision. Inevitably, the weight of an error will depend on the extent to which it affects the decision. An error that is peripheral to the administrative decision-maker’s reasoning process, or overcome by more compelling points advanced in support of the result, does not provide fertile ground for judicial review.Absent an assessment of materiality, disappointed litigants would have an incentive to engage in a "“line-by-line treasure hunt for error”" so as to be in a position to argue that the decision was unreasonable based on the sheer volume of errors, however trivial. There appears to be an element of this in Bell’s approach to this case.
Vavilov at para. 300