Skip to content.

The Heat Is On: The Justiciability Of Climate Claims

A recent Ontario decision held that, among other things, climate-related challenges are justiciable, opening up (at least) the possibility of increased climate change litigation in Canada.

In Mathur v. His Majesty the King in Right of Ontario,[1] a group of seven young climate change activists commenced a constitutional challenge against the Ontario government in response to legislation that substantially weakened targets for the reduction of greenhouse gas (“GHG”) emissions in the province. The applicant-activists argued that Ontario’s adoption of weaker GHG reduction targets would lead to climate catastrophe, violating the rights of Ontario youth and future generations under Sections 7 (life, liberty and security of the person) and 15 (equality) of the Canadian Charter of Rights and Freedoms. In response, Ontario filed a motion to dismiss the activists’ challenge, arguing that the subject matter of the litigation was a policy decision that was not reviewable by the court.

Although the climate change activists in Mathur were not successful on the merits of their Charter challenge, Justice Vermette of the Ontario Superior Court of Justice held that climate change lawsuits are nonetheless justiciable, meaning that they are suitable for determination by a court. Mathur leaves open the possibility, perhaps even likelihood, of future climate change litigation against governments in Canada. Moreover, Ecojustice has announced that the applicant-activists in Mathur plan to appeal the decision on the merits.[2]

Although Mathur is the first Ontario decision to find that climate-related claims are justiciable, the decision comes on the heels of a British Columbia Supreme Court decision, in Sierra Club of British Columbia Foundation v. British Columbia (Minister of Environment and Climate Change Strategy), that similarly concluded a climate-related claim was justiciable (but the BC Government’s challenged climate change accountability reports were reasonable).[3] Our summary of Justice Basran’s decision in Sierra Club can be found here.

These findings of justiciability are significant developments on the frontier of climate-related litigation in Canada, particularly where applications and claims are brought in an effort to hold governments accountable. We anticipate further develops to the doctrine of justiciability in the context of Canadian climate-related litigation.


On October 31, 2018, Bill 4[4] enacting the Cap and Trade Cancellation Act (the “CTCA”) received royal assent.[5] Section 3(1) of the CTCA provides that the Government of Ontario shall establish targets for the reduction of GHG emissions in the province.[6] Section 16 of the CTCA repealed a previous GHG reduction target (37% below 1990 levels by the end of 2030),[7] replacing it with a target of 30% below 2005 levels by 2030.[8]

The applicants in Mathur challenged the revised GHG reduction target, arguing that it was unconstitutional on the basis that it violated the applicants’ right to life and security of the person under Section 7 of the Canadian Charter of Rights and Freedoms as well as their equality rights under Section 15 of the Charter.[9]

The applicants’ Section 7 claim was premised on the argument that “climate change poses dangerous and existential risks to the life and well-being of Ontarians and the world”, thereby sufficiently engaging the interests protected by this section of the Charter.[10] Further, the applicants argued that Ontario’s new GHG reduction target created a distinction based on the enumerated ground of age, contrary to Section 15, as:

  1. young people are particularly susceptible to negative physical health impacts resulting from climate change, and youth will bear a disproportionate impact of the mental health impacts of climate change;
  2. the catastrophic impacts of climate change will worsen over time as global temperatures continue to rise, and by virtue of their age, youth and future generations will bear the brunt of these impacts as they live longer into the future; and
  3. young people’s liberty and future life choices are being constrained by decisions being made today over which they have no control.[11]

Notably, the Government of Ontario did not contest the anthropogenic nature of global climate change, its risks to human health and well-being, nor the desirability of taking action to mitigate its adverse effects.[12]

The Decision

Justice Vermette dismissed the application, finding that there were no violations of Sections 7 and 15 of the Charter.[13] The Court noted that the Charter does not bind legislatures to their current policies, and with respect to Section 16 of the CTCA, the Court held that “a mere change in the law cannot be the basis for a Charter violation . . . even if the previous law provided greater life, liberty or security of the person.”[14]

The Court found that the applicants’ Section 7 rights were engaged, but that the applicants failed to demonstrate that any deprivations were contrary to the principles of fundamental justice.[15] Thus, no violation of Section 7 was established. With respect to the applicants’ Section 15 claim, Justice Vermette accepted that young people are disproportionately impacted by climate change, but concluded this was due to climate change in and of itself, and not due to the CTCA, the revised GHG reduction target, or Ontario’s climate plan.[16] Referencing the Supreme Court of Canada’s 2022 decision in R. v. Sharma, the Court provided the latest reminder that Section 15(1) of the Charter does not impose general positive obligations on the state to remedy inequalities or enact remedial legislation.[17]

While the applicants were not successful in advancing their Charter claims, the Court considered the Charter issues, lending the Charter challenge legitimacy.[18] Further, the Court unequivocally accepted the stark realities of climate change, referencing extensively to the Supreme Court of Canada’s 2021 decision in References re Greenhouse Gas Pollution Pricing Act (“GGPPA”), which found “it is well-established that climate change is causing significant environmental, economic, and human harm, nationally and internationally…”[19] Justice Vermette was also plainly critical of the province’s climate efforts, finding that they fall “severely short” of what has been identified as necessary by scientific consensus.[20]

The Climate Litigation Landscape Post-Mathur and other Recent Decisions

Mathur, and Sierra Club before it, present significant advances for individuals concerned with government (in)action as it relates to climate change and its effects. In Sierra Club, Justice Basran of the Supreme Court of British Columbia held that the Climate Change Accountability Act[21] imposes justiciable statutory reporting obligations on climate change targets.[22] As we noted previously, Sierra Club’s finding that courts can enforce reporting obligations leaves the door open for judicial oversight in that context.

Notably, Mathur and Sierra Club depart from recent Canadian decisions holding that challenges to the entirety of Canada’s GHG reduction conduct and its cumulative effects are not justiciable.[23] Concurrent appeals in two such cases, La Rose v. Canada, 2020 FC 1008, and Misdzi Yikh v. Canada, 2020 FC 1059, have taken place and decisions from the Federal Court of Appeal are forthcoming. With an appeal in Mathur announced by Ecojustice, it is all but certain that climate change litigation is only getting started in Canada.

The rise in climate-related litigation in Canada is also reflected abroad, and in particular in the United States. There are two significant climate change lawsuits similar to Mathur and Sierra Club underway in the U.S.: Juliana v. United States (“Juliana”)[24] and Held v. State of Montana (“Held”).[25] In Juliana, an application brought by twenty-one young Americans, it was asserted that the government’s actions violated the applicants’ constitutional right to a climate system capable of sustaining human life.[26] In Juliana, the United States Court of Appeals for the Ninth Circuit held there was no explicit right to a stable climate system in the United States Constitution, making the matter non-justiciable.[27] However, the applicants successfully amended their complaint on June 1, 2023, allowing them to move forward to trial.[28] Held, a case in which sixteen young Montanans are suing the state government in relation to fossil fuel extraction and burning, is the first constitutional climate case in the United States to successfully make it to trial.[29] The trial in Held recently concluded and a ruling is expected in the coming months. No matter the outcome, we anticipate that the ruling will be appealed to the Montana Supreme Court.

Decisions such as Mathur, Sierra Club, Juliana, and Held highlight how both social and judicial perceptions of climate change and its impact are evolving both inside and outside courtrooms. Further developments related to climate change litigation will undoubtedly present themselves, including in the private sector context, as regulations regarding climate-related financial disclosures (such as proposed National Instrument 51-107 – Disclosure of Climate-related Matters, which we reviewed here) come into effect. Regulatory processes in Canada have already been leveraged to bring climate-related action in the private sector, such as through greenwashing allegations investigated by the Competition Bureau.


Although the Applicants in Mathur were not successful in their Charter challenge, the Court was not entirely unsympathetic to their arguments. The key takeaway from Mathur is the finding that the Charter issues raised by the applicants are justiciable – signalling that government climate action (or inaction, as the case may be) can be justiciable where specific state action or legislation is challenged.[30] The Court also left room for future cases to argue the application of positive obligations on governments under Section 7 of the Charter:

[T]he Applicants make a compelling case that climate change and the existential threat that it poses to human life and security of the person present special circumstances that could justify the imposition of positive obligations under section 7 of the Charter . . . the Federal Court of Appeal has recognized that section 7 is not frozen in time and that, some day, it may evolve to encompass positive obligations, possibly in the domain of “climate rights”, among others. . . .[31]

Mathur provides important insights for future climate-related litigation, especially in Ontario: (1) constitutional challenges to government climate actions must target specific government actions or legislation in order to be justiciable, as broad allegations of policy and pan-Canadian inaction will be held non-justiciable; (2) climate change concerns may lead to the imposition of positive obligations under Section 7 of the Charter; and (3) climate change actions against the government will be difficult to prove and a successful action may be many years away.

We are here to help

McCarthy Tétrault has a multidisciplinary ESG and Sustainability team that is equipped to provide clients with a full suite of advice and support to assist them in integrating ESG thinking into their organizational DNA. With a robust understanding of business, industry, and market drivers, we are well-suited to provide contextualized guidance. Please contact Robert Richardson, Sonia Struthers, or any of the authors of this article if you have any questions regarding ESG-linked lending.


[1] 2023 ONSC 2316 (“Mathur”).

[2] Ecojustice, “Statement: Ontario youth undeterred in legal fight to hold Ontario government accountable for climate action” (18 April 2023), online: <> [].

[3] 2023 BCSC 74 (“Sierra Club”).

[4] Legislative Assembly of Ontario, “Bill 4, Cap and Trade Cancellation Act, 2018” (last visited 20 June 2023), online: <> [].

[5] Cap and Trade Cancellation Act, 2018, SO 2018, c 13.

[6] Ibid, s 3(1).

[7] Ibid, s 16.

[8] Environmental Registry of Ontario, “Preserving and Protecting our Environment for Future Generations: A Made-in-Ontario Environment Plan” (last visited 20 June 2023), online: <,communities%20and%20families%20prepare%20for> [].

[9] Mathur, supra note 1 at paras 48, 68.

[10] Ibid at para 48.

[11] Ibid at para 177.

[12] Ibid at para 4.

[13] Ibid at para 5.

[14] Ibid at paras 114-16.

[15] Ibid at para 171.

[16] Ibid at para 178.

[17] Ibid.

[18] Ibid at para 106.

[19] References re Greenhouse Gas Pollution Pricing Act, 2021 SCC 11 at para 187.

[20] Mathur, supra note 1 at para 147.

[21] Climate Change Accountability Act, SBC 2007, c 42.

[22] Sierra Club, supra note 2.

[23] La Rose v Canada, 2020 FC 1008 at paras 22, 26, 102; Misdzi Yikh v Canada, 2020 FC 1059; Environnement Jeunesse c Procureur général du Canada, 2021 QCCA 1871.

[24] Juliana v United States, 947 F (3d) 1159 (9th Cir 2020).

[25] Climate Change Litigation Database, “Held v. State” (last visited 27 June 2023), online (pdf): <> [].

[26] United States Court of Appeals for the Ninth Circuit, “Juliana v. United States” (17 January 2020) at 11, online (pdf): <> [].

[27] Ibid at 30, 32.

[28] United States District Court for the District of Oregon Eugene Division, “Opinion and Order” (1 June 2023) at 19, online (pdf): <> [].

[29] YouthvGov, “Historic Climate Trial: Held v. State of Montana” (last visited 20 June 2023), online: <> [].

[30] Mathur, supra note 1 at para 106.

[31] Ibid at para 138.