Appeals - Standard of Review (SOR) - Extricable Issues of LawVavilov [para 37] makes the point that we should separate 'readily extricable principles of law' from mixed issues of fact and law wherever possible.
. 1475182 Ontario Inc. o/a Edges Contracting v. Ghotbi
In 1475182 Ontario Inc. o/a Edges Contracting v. Ghotbi (Div Ct, 2021) the Divisional Court set out examples of 'extricable question of law' drawn from mixed fact and law issues:
 More difficult are questions of mixed fact and law, which involve the application of a legal standard to a set of facts. Generally, the standard of review is palpable and overriding error. But where there is an extricable question of law, such as a where the decision-maker applies an incorrect standard, fails to consider a required element of a legal test or makes a similar error in principle, then the error is properly characterized as an error of law and the applicable standard of review is correctness. See Housen, para. 36.. Neptune Wellness Solutions v. Canada (Border Services Agency)
In Neptune Wellness Solutions v. Canada (Border Services Agency) (Fed CA, 2020) the Federal Court of Appeal discussed the nature of an 'extricable question of law embedded in a question of mixed fact and law', for standard of review purposes:
 The Court must examine the specific grounds of appeal to ensure they in fact raise a question of law, and not questions of fact or of mixed fact and law masquerading as questions of law. The challenge lies in those cases where there is an extricable question of law embedded in a question of mixed fact and law. Guidance as to how to discern questions of law from a question of mixed fact and law is found in the decision of this Court in Canadian National Railway v. Emerson Milling Inc., 2017 FCA 79 at paras. 24-28,  2 F.C.R. 573, where the Court provided examples of what constitutes an extricable question of law embedded in a question of mixed fact and law:
26 […] Extricable questions of law/legal standards are best regarded as questions of law of the sort intended by Parliament to be reviewed by this Court under subsection 41(1). In a number of cases, this Court determined appeals where extricable questions of law/legal standards (in addition to other legal and jurisdictional questions) were present: More recently, in Bell Canada v. British Columbia Broadband Association, 2020 FCA 140 at paras. 49-51, the Court noted that a question of law may also be factually infused, as in the case of procedural fairness. In all cases, it is the true substance of the question on appeal that governs, and not the form by which it is expressed. Examination of the notice of appeal and the memoranda of fact and law assist in determining the essential character of the issue.
• Canadian National Railway v. Canadian Transportation Agency, 2010 FCA 65,  3 F.C.R. 264 (F.C.A.) (CN 2010) and Canadian National Railway v. Canadian Transportation Agency, 2008 FCA 363, 383 N.R. 349 (F.C.A.) (CN 2008). What matters fall into certain defined terms in the Act, triggering the revenue cap in the Act? The extricable legal question was the definition of the defined terms in the Act.
• Dreyfus, above at para. 18. Two issues were raised that involve extricable questions of law, namely statutory interpretation. Does the "evaluation approach," a methodology adopted by the Agency for deciding questions under sections 113-116, deviate from the proper interpretation of the sections? Did the Agency fail to consider matters that the statute requires it to consider?
• Canadian National Railway v. Richardson International Ltd., 2015 FCA 180, 476 N.R. 83 (F.C.A.). Do the facts of the case constitute a "line of railway" and a "connection" for the purposes of triggering the carrier's interswitching obligations? The extricable question of law was the meaning of these terms.
• Canadian National Railway v. Viterra Inc., 2017 FCA 6 (F.C.A.). On the facts, were the obligations of the carrier under section 113 triggered? Was the carrier's rationing methodology a confidential contract under subsection 113(4) of the Act?