Environmental Law: Mathur v. Ontario
- LSOU Publications
- 32 minutes ago
- 4 min read
Written By: Jissana Ahad
Legal Terms
1. Justiciable: a matter appropriate for court decision
2. Remitted: when a higher court returns a case to a lower court
3. Statutory Obligation: a duty created by law
4. Cap-and-Trade System: a policy limiting emissions through tradable allowances
5. Climate Governance: government control and accountability over climate action
Case Name & Citation
Mathur v. Ontario, ONCA 762 [2024]
Facts
A group of seven young climate activists in Ontario, aged 12–24, brought a constitutional challenge against the Government of Ontario under sections 7 (life, liberty, and security of the person) and 15 (equality rights) of the Canadian Charter of Rights and Freedoms. They argued that Ontario’s 2018 climate legislation, enacted through the Cap and Trade Cancellation Act and the new “Ontario Target,” weakened the province’s earlier emission-reduction commitments by setting a substantially lower goal for 2030. Ontario’s 2016 law had set a stronger target of 37% below 1990 levels by 2030, which the 2018 “Ontario Target” replaced with a weaker goal. The applicants claimed this regression left them disproportionately vulnerable to the “existential” risks of climate change, particularly as young people who will face its long-term consequences.
The dispute arose after Ontario repealed its cap-and-trade system and adopted a less ambitious climate plan. The applicants contended that this reversal undermined previous progress on emission reductions and exposed them and future generations to greater environmental and health harms, forming the foundation of their constitutional challenge. The court noted that Ontario argued climate policy falls within the realm of government discretion and is not a justiciable Charter matter, emphasizing that the Charter does not impose positive obligations on governments to protect individuals from climate change.
Procedural Posture
When the case was first heard at the Ontario Superior Court of Justice (2023 ONSC 2316), the trial judge dismissed the youth applicants’ Charter claims, finding that the Charter did not compel Ontario to enact or maintain stronger climate policies. On appeal, the Ontario Court of Appeal (2024 ONCA 762) found that the lower court had mischaracterized the applicants’ argument. The appellate court clarified that the applicants were not asking the government to take on new duties, but rather challenging whether Ontario’s existing climate legislation met its constitutional obligations. The Court therefore set aside the dismissal and remitted the case to the Superior Court for reconsideration under this proper framework.
Issue
Whether Ontario’s legislated climate plan and greenhouse-gas emission-reduction target, adopted under its own environmental legislation, violate the applicants’ rights under section 7 and section 15 of the Canadian Charter of Rights and Freedoms by failing to adequately protect against the harms of climate change. The central dispute is if Ontario’s voluntarily assumed statutory obligation to combat climate change allows its weakened emissions-reduction target to be constitutionally scrutinized under the Charter.
Rule Applied
The Court grounded its analysis in sections 7 and 15 of the Canadian Charter of Rights and Freedoms, interpreting these rights within the context of Ontario’s self-imposed statutory commitment to address climate change. It emphasized that while the Charter does not generally create new governmental duties, once a province enacts climate legislation, the implementation and targets within that framework must still align with constitutional protections. The Court held that Ontario’s climate-target legislation, once enacted, created a statutory obligation subject to Charter scrutiny, meaning the government’s chosen target must align with constitutional rights.
Holding
The Ontario Court of Appeal determined that the youth applicants’ Charter challenge was proper for judicial review, finding that the trial judge erred in dismissing the claim. The Court held that once Ontario legislated a climate plan, it assumed a constitutional responsibility to ensure that its emission-reduction target and related policies conform to the Canadian Charter of Rights and Freedoms. Accordingly, the Court overturned the lower court’s ruling and returned the matter to the Superior Court of Justice to reassess the case under the correct legal framework, focusing on whether Ontario’s climate plan fulfills its Charter-compliant statutory obligations to address climate change.
Reasoning
The Court of Appeal concluded that the trial judge misunderstood the nature of the applicants’ claim. Rather than attempting to impose new governmental duties, the applicants were challenging how Ontario fulfilled the responsibilities it had already assumed under its own climate legislation. By passing the Cap and Trade Cancellation Act and adopting the “Ontario Target,” the province had effectively committed itself to addressing climate change in a manner consistent with the Charter of Rights and Freedoms. The Court emphasized that the applicants’ claim was about ensuring constitutional compliance within an existing statutory framework, not expanding the scope of government obligations.
In reaching this conclusion, the Court emphasized the unique and far-reaching nature of climate change while exercising judicial restraint, limiting its review to whether Ontario’s legislated plan met its Charter obligations. It referenced prior Supreme Court cases, including Gosselin v. Québec (2002) and Tanudjaja v. Canada (2014), to clarify when courts may review alleged government inaction in social or environmental policy contexts. Both cases limited judicial review of broad policy inaction but allowed it when tied to concrete statutory or constitutional duties, as in Mathur.
Result
The Ontario Court of Appeal overturned the lower court’s dismissal and sent the case back for reconsideration under the proper Charter framework. Its decision confirmed that once a government legislates on climate change, the resulting targets and plans must comply with constitutional rights.The Supreme Court of Canada’s refusal to hear a further appeal on May 1, 2025, made this ruling final in Ontario and persuasive across Canada. The outcome strengthened the applicants’ position while signalling to governments that climate legislation is subject to Charter scrutiny.
Concurrences & Dissents
The decision was unanimous, with no separate concurring or dissenting opinions issued. The Ontario Court of Appeal spoke with one voice, emphasizing that Ontario’s climate legislation, having been voluntarily enacted, must be assessed for Charter compliance. The ruling underscored that true constitutional accountability in climate governance comes from holding governments to the commitments they have already made.
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