Mootness - Standard of Review. Peckford v. Canada (Attorney General)
In Peckford v. Canada (Attorney General) (Fed CA, 2023) the Federal Court of Appeal considered four related appeals from dismissed JRs against requirements that "air and rail travellers to be vaccinated against COVID-19", which were dismissed for mootness as the policy was spent.
In this quote the court addressed the SOR for mootness issues:
 Even on the issues that are properly before this Court for consideration, the appellants’ written arguments generally fail to recognize that we must apply the appellate standards of review. Except on pure questions of law, we will not interfere with the Federal Court’s decision in the absence of a palpable and overriding error. This is a highly deferential standard. As stated in Plato v. Canada (National Revenue), 2015 FCA 217 at para. 4:. DeGroot v. Licence Appeal Tribunal
The identification of the legal factors to determine if a case is moot is a question of law reviewable under the standard of correctness (Canada (Fisheries and Oceans) v. David Suzuki Foundation, 2012 FCA 40,  4 F.C.R. 155, at paragraph 57). Once it is established that a case is moot, the Judge has a broad discretion to hear the matter or not, but must properly weigh the criteria established in Borowski v. Canada (Attorney General), 1989 CanLII 123 (SCC),  1 S.C.R. 342, (Borowski). This fine exercise of balancing is a mixed question of facts and law. Deference is owed to that decision.
In DeGroot v. Licence Appeal Tribunal (Div Court, 2022) the Divisional Court considered an appeal from a matter that the tribunal below had deemed moot as a matter of discretion, and held that a deferential standard of review applied:
 As it relates to the question of mootness, the decision of whether to hear and decide a moot issue is one which is an exercise of discretion. This court must therefore defer to the exercise of the LAT’s discretion unless the decision of the Adjudicator was unreasonable; was based on irrelevant or extraneous considerations; was based on a wrong principle, or where no weight had been given to a relevant consideration. - See Canadian Pacific Ltd. v. Matsqui Indian Band 1995 CanLII 145 (SCC),  1 SCR 3 at paras. 39 and 112; Volochay v. College of Massage Therapists of Ontario 2012 ONCA 541 at para. 52; Strickland v. Canada (Attorney General) 2015 SCC 27 at para. 39; and Ball v. McAulay 2020 ONCA 481 at paras. 118 and 124.