Skip to content.

Supreme Court of Canada Clarifies the Role of Interveners

An intervention is a procedural device that allows a non-party to participate in a proceeding.[1] At the Supreme Court of Canada, interventions have become routine. For example, between 2015 and 2018, about two thirds of Supreme Court proceedings featured at least one intervener, and an average of 252 interveners — including corporations, trade associations, non-profits, and individuals — appeared before the Court each year.[2] These statistics reflect the integral role interveners play in Supreme Court cases, which often have broader impacts beyond the parties to the dispute. Below, we summarize the intervention process, the Supreme Court’s recent guidance on the role of interveners, three practical intervention tips, and how we can help.

What is an intervention?

The Rules of the Supreme Court of Canada[3] (the “Rules”) govern the Supreme Court intervention process. Under the Rules, any person interested in an application for leave to appeal, an appeal, or a reference to the Supreme Court may apply for intervener status.[4] In the case of an appeal, the proposed intervener must bring its application within four weeks after the appellant has filed its factum.[5] This application must set out the proposed intervener’s relevant expertise or experience, its interest in the proceeding, and its proposed submissions.[6]

The Supreme Court enjoys a wide discretion in deciding whether, and on what terms, to allow a proposed intervention.[7] At a minimum, however, the applicant must show that it: (1) has an interest in the proceeding; and (2) will make submissions that are both useful and different from the parties’ submissions.[8] To illustrate, an applicant may meet the first criterion by showing that it “represent[s] an interest which is directly affected by the appeal”,[9] and may meet the second criterion by showing that it has “a history of involvement in the issue giving the applicant an expertise which can shed fresh light or provide new information on the matter”.[10]  

Since the Charter’s enactment in 1982, the Supreme Court has granted intervener status increasingly liberally.[11] In a typical year, the Supreme Court grants over 90% of intervention motions.[12] In deciding whether to allow an intervention, the Supreme Court must weigh the goal of preserving scarce judicial resources against the goal of permitting interested individuals and groups to be engaged in the judicial process, and the value to the Court of that engagement.

If the Court grants an intervention, it may set the terms of that intervention.[13] Often, interveners are permitted to make brief written submissions (typically 20 pages for an attorney general in a constitutional case, and 10 pages for any other intervener[14]) and brief oral submissions (typically 10 minutes for an attorney general in a constitutional case, and 5 minutes for any other intervener). However, interveners are not permitted to raise new issues on appeal, unless expressly permitted by the Court.[15] Nor are they permitted to seek costs from the parties. By contrast, parties have a right to seek reimbursement from an intervener for any additional disbursements incurred as a result of the intervention, though this right is rarely, if ever, exercised.[16]

Interventions matter. Studies have shown interventions have a statistically significant impact on judicial decision making,[17] and the Supreme Court often expressly relies on interveners’ submissions in its reasons for judgment. In fact, the Court recently declined to provide guidance on certain legal issues in “the absence of interveners who could shed light on them”.[18]

The Court has clarified the role of interveners

On November 15, 2021, the Supreme Court of Canada released a notice setting out “the Court’s expectations of interveners, and the scope of their submissions, in cases before it”:

  1. The Court expects all intervener submissions to be useful to the Court and different from those of the parties.
  2. The purpose of an intervention is not to support a party but to advance the intervener’s own view of a legal issue before the Court. Despite the participation of interveners, the case remains a dispute between its parties. However, the fact that an intervener’s submission aligns it generally with one party over another does not, without more, make the submission inappropriate.
  3. Interveners should not take a position on the outcome of an appeal, whether in written or oral argument.
  4. Interveners must not challenge findings of fact, introduce new issues, or try to expand the case.
  5. In considering applications to intervene, the Court will be mindful of the need not to unduly imbalance the arguments before it.
  6. The Court always retains a discretion to take any steps it sees fit to prevent an unfairness to the parties arising from an intervener’s participation in an appeal.

These stated expectations summarize and clarify rules and principles reflected in the Rules and the Court’s case law. They put interveners on notice not to exceed the limits of their role, and may signal that the Court will strictly enforce those limits. Prospective interveners should take heed.

How to make the most of a proposed intervention

Intervening in appeals to the Supreme Court of Canada offers interested groups and individuals a valuable opportunity to help shape the law by making useful and different submissions. To use this opportunity effectively, we offer the following practical tips for successful interventions:

  1. Be helpful. Interveners should aim to be as helpful as possible. Interveners can assist the Court in a number of ways, such as by: providing a unique perspective on the issues raised (without supplementing the record) based on the intervener’s particular expertise and experience; making submissions that address how a particular decision has played out or may play out in other contexts and cases; and/or highlighting the potential impact of a decision on parties not before the Court.
  2. Pick your battles. Interveners often have unique and specialized capabilities, ranging from practical know-how to policy expertise. But these capabilities often relate only to some issues in a case. Rather than take a position on all the issues before the Court, interveners should focus on the issue(s) that matter(s) the most to them, and on which they can have the greatest impact.
  3. Stick to the issues before the Court. Interveners must restrict themselves to the issues already before the Court. They cannot add new claims or raise new issues. Even if an intervener has a useful and different perspective to offer, the Court will not hear that perspective if it is clouded by improper submissions addressing new issues beyond the scope of the appeal.

We can help

Our National Appellate Litigation Group regularly represents interveners before the Supreme Court of Canada. If you have questions about our appellate practice, our experience in Supreme Court matters, or a potential intervention, please contact Brandon Kain or Adam Goldenberg.


[1] Paul R. Muldoon, Law of Intervention (Aurora, Ont.: Canada Law Book, 1989), at 3.

[2] Geoffrey D. Callaghan, “Intervenors at the Supreme Court of Canada” (2020) 43:1 Dal. L.J. 33, at 34.

[3] Rules of the Supreme Court of Canada, S.O.R./2002-156 [Rules].

[4] Rules, r. 55.

[5] Rules, r. 56.

[6] Rules, r. 57.

[7] Norcan Ltd. v. Lebrock, [1969] S.C.R. 665, at 666-67; Reference re Workers’ Compensation Act 1983 (Nfld.), [1989] 2 S.C.R. 335 (Chambers) [Workers’ Compensation], at 339.

[8] Workers’ Compensation (S.C.C., 1989), supra note 7, at 339; R. v. Finta, [1993] 1 S.C.R. 1138 (Chambers) [Finta], at 1142.

[9] Finta (S.C.C., 1993), supra note 8, at 1143.

[10] Workers’ Compensation (S.C.C., 1989), supra note 7, at 340.

[11] Amanda Jane Burgess, Intervenors Before the Supreme Court of Canada, 1997-1999: A Content Analysis (National Library of Canada, 2000), at 9-10.

[12] Benjamin R.D. Alaire & Andrew J. Green, “Interventions at the Supreme Court of Canada: Accuracy, Affiliation, and Acceptance” (2010) 48:3 Osgoode Hall L.J. 381, at 383.

[13] Rules, r. 59(1).

[14] Rules, r. 42(5).

[15] Rules, r. 59(3).

[16] Rules, r. 59(1)(a).

[17] Alaire & Green, supra note 12, at 405-10.

[18] R. v. Yusuf, 2021 SCC 2, at para. 5.



Stay Connected

Get the latest posts from this blog

Please enter a valid email address