Every few decades, a court case comes along that confronts the most urgent challenge of its time. Mathur et al. v. His Majesty the King in Right of Ontario is one of those cases.
Since this youth-led, precedent-setting case was launched, it has overcome legal hurdles, government attempts to have it thrown out of court, and is on the verge of changing our law and our society all across Canada.
At any moment, Mathur will become the first citizen-led climate case to be heard at the Supreme Court of Canada or be put on the fast track for a decisive final hearing in Ontario. Either way we believe the Mathur case is primed to deliver a momentous victory for climate action under our Constitution.
As we continue forward, I reflect on what led us to this point — and the history we have made along the way.
The beginning of the beginning of the Mathur case
Do you ever feel like lawsuits seem to go on forever? You are not alone.
Way back in June 2015, a court in the Netherlands made a groundbreaking decision in the Urgenda case, ruling that the Dutch government had to meet greenhouse gas pollution goals based on the international scientific consensus. In other words, the government could choose how to meet the science-based goals in a way that made sense for Dutch society, but it could not do less than the scientifically determined minimum without violating the rights of its citizens.
Straight away, lawyers around the world started thinking about how to argue for a similar precedent in their own countries, each with their own unique legal systems. I was one of them and you can still read my blog from a decade ago on what the Urgenda case could mean for Canada.
Alongside my colleagues Fraser Thomson, Julia Croome, and others at Ecojustice, I spent the next few years thinking through how a citizen-led climate case could work in Canada. At that time, no such case had ever reached a hearing on the merits. We knew many legal hurdles lay ahead of us. We began planning for them.
Fast forward to 2018-2019, and the youth-led, global “climate strike” protest movement was sweeping the world. In Canada, the first youth to walk out of class and demand the adults act like adults during the climate crisis was 11-year-old Sophia Mathur from Sudbury, Ontario.
Around the same time, the Ontario government chose this moment to severely weaken its 2030 climate target for reducing greenhouse gas pollution. I met Sophia that winter and, before long, she and six other courageous Ontario youth had enlisted Ecojustice to represent them — free of charge. We were going to sue the Ontario government for violating the young activists’ constitutional rights under the Charter to life, security of the person, and equality — by severely weakening Ontario’s 2030 target for reducing greenhouse gas pollution.
I will come back to this story in a minute but first, let me tell you how I think about time when I’m thinking about climate lawsuits.
Climate change as a clock
Think of a clock. One of those old analog clocks. The hands of a clock are one way to understand the different cycles over which the climate change challenge is playing out in 2025.
On a clock, the seconds hand ticks, ticks, ticks along at a ceaseless pace; the minutes hand makes slow but steady progress; while the hours hand seems like it barely moves but makes all the difference.
With climate politics in 2025, the cycle driving legislation and government spending on climate action is moving at a furious pace — it is that seconds hand whizzing around the dial. Realistically, we hope for climate progress at the pace of two steps forward, one step back, but climate politics sometimes accelerates for better and worse. In the Trump era, there seems to be a new thing whipsawing the story of climate politics every day.
Then there’s climate litigation. Citizen-led climate lawsuits are a real source of hope when governments won’t deliver, but these cases require patience — they are the minutes hand, making slow but visible progress. Lawyers build up the evidence and arguments across years of courtroom showdowns, leading to legal precedents that can hold governments and corporations to account and influence a years-long transition of our society and economy away from fossil fuels and toward a clean energy future.
Finally, there’s the changing climate itself, which plays out across centuries and millennia — this is the hours hand. Since the industrial revolution, we’ve been burning evermore coal, oil, and gas for energy, unlocking geological carbon that formed over millions of years and pumping it into our present-day atmosphere in the blink of a geological eye. Every new tonne of carbon dioxide we throw up there will keep warming our planet for centuries. The results are the wildfires, floods, heatwaves, and rising sea levels that are already bad and will increasingly burden every human generation and the natural world until we get off fossil fuels and reach “net zero” carbon pollution.
The different timescales across which the climate crisis operates can be disorienting but they are important to remember. If the politics of the day do not swing toward progress, we can continue fighting for climate action in the courts — even if it takes longer. And the physics of climate change mean that every tonne of carbon dioxide we stop from getting into the atmosphere — from now until we reach net zero — is a tonne that won’t burden our kids and grandkids.
At Ecojustice, we have our eye on the long game and we aim to hold our governments and corporations accountable for science-based climate action. By bringing science into the courtroom and representing clients with ringing claims to justice we seek legal precedents that can guide Canada to a climate-safe future.
The Mathur case and its momentous final act
Back to the story. Since the youth filed their case in November 2019 there have been many twists and turns, but we have never lost sight of the goal: a historic precedent for constitutional rights in the context of the climate crisis.
As a first move, the youth filed the most extensive evidentiary record of how climate change will impact Canadians that has ever been put before a Canadian court. Seventeen expert witnesses detailed for the court all of the ways in which climate change is impacting (and will continue to impact) the physical and mental health of Ontario youth. The evidence showed that “it is indisputable that, as a result of climate change, the Applicants and Ontarians in general are experiencing an increased risk of death and an increased risk to the security of the person.”
Ontario’s first countermove was not to defend its weaker target as based in science, or consistent with the Constitution. Instead, Ontario tried to have a judge throw out the case on preliminary grounds. We fought back and in 2021, the youth won their right to have their day in court — the first time a citizen-led climate case would be heard on its merits in Canada. The Mathur case could not have had this initial success where earlier cases had failed without diligent and patient legal work, enabled by generous and committed donors.
Everyone was disappointed as the case suffered a setback in April 2023, when the court sided with the youth on many issues but ultimately adopted Ontario’s legal argument that the youth were asserting “positive rights” not yet recognized under the Charter.
But you know what happened next?
Undeterred, the youth appealed and in October 2024, a unanimous three-judge panel at the Ontario Court of Appeal made a landmark decision knocking out Ontario’s positive rights argument and ordering a new hearing before the trial court.
With its main argument dashed, Ontario sought leave to appeal to the Supreme Court of Canada (it is not automatic) and in January we filed a cross-appeal for the youth seeking an urgent and final decision of the case in favour of the youth on all points. Soon, we will learn if the Supreme Court will be taking up the case.
So here we stand in April 2025, on the precipice of a historic, youth-driven win for climate rights under our Constitution. We believe that a win is coming, whether at the Supreme Court of Canada or back here in the courts of Ontario. And when it does it will be a gamechanger for climate action in Canada.
Slow and steady will win the race for climate justice
It’s been over five years since the Mathur case was filed and nearly a decade since Ecojustice lawyers first started laying the legal groundwork for its success.
There are many ways to count the time.
When I started thinking about citizen-led climate cases I considered myself part of “younger generations” — now I have three kids of my own. When the youth case was filed, Sophia Mathur was a middle schooler — now she’s getting ready to vote in her first election. When Ontario weakened its 2030 GHG target there were twelve years left to do the right thing and recommit to science-based climate action — now there are four and a half.
But the thing with climate change is it’s never too late to do the right thing for our kids and our country.
By leaving behind yesterday’s fossil fuel economy for tomorrow’s clean energy future, we can harness Canada’s enormous potential for renewable energy and build an energy economy that makes us healthier, wealthier, and less dependent on volatile international fossil fuel markets. As we do this, every tonne of carbon we can stop from reaching the atmosphere is another problem that today’s youth won’t have to deal with, and their kids, and their kids, and so on.
As the saying goes, “the wheels of justice turn slowly.” When it comes to climate litigation in Canada those wheels are slowly but surely rolling toward a legal reckoning for governments and corporations that would ignore the rights of youth and let our planet burn.
Ecojustice has been leading this fight in the courts for the last ten years and we will continue to. It will take time, but we will always do our part to secure a safe climate future for all. It will take time, but together we can beat the clock.
