On June 28, 2019, the Ontario Court of Appeal released its decision in Reference re Greenhouse Gas Pollution Pricing Act, 2019 ONCA 544. By a four-to-one verdict, the Court of Appeal concluded the federal Greenhouse Gas Pollution Pricing Act was within the constitutional powers of Parliament. The judgement was rendered by five justices of the Court of Appeal: Strathy C.J.O. (for the majority); MacPherson J.A. (concurring with Strathy); Sharpe J.A. (concurring with Strathy); Hoy A.C.J.O. (concurring judgement); and Huscroft J.A. (dissenting).
According to Strathy C.J.O.:
 The Act is within Parliament’s jurisdiction to legislate in relation to matters of “national concern” under the “Peace, Order, and good Government” (“POGG”) clause of s. 91 of the Constitution Act, 1867. Parliament has determined that atmospheric accumulation of greenhouse gases (“GHGs”) causes climate changes that pose an existential threat to human civilization and the global ecosystem. The impact on Canada, especially in coastal regions and in the north, is considered particularly acute.
 The need for a collective approach to a matter of national concern, and the risk of non-participation by one or more provinces, permits Canada to adopt minimum national standards to reduce GHG emissions. The Act does this and no more. It leaves ample scope for provincial legislation in relation to the environment, climate change and GHGs, while narrowly constraining federal jurisdiction to address the risk of provincial inaction.
 The charges imposed by the Act are themselves constitutional. They are regulatory in nature and connected to the purposes of the Act. They are not taxes.
In dissent, Huscroft J.A. wrote:
 … I conclude that Parts 1 and 2 of the Act are not valid exercises of the national concern branch of the POGG power. The constitutionality of Parts 3 and 4 of the Act is not challenged.
 I conclude with a brief comment on Parliament’s lawmaking authority.
 The key point is this: my conclusion that passage of the Act is not authorized under the national concern branch of the POGG power does not mean that Parliament is powerless to address climate change. On the contrary, Parliament has significant authority to address pollution and the environment, including lawmaking authority over taxation, criminal law, and trade and commerce – none of which have been exercised here. Not only can Parliament legislate in a variety of ways to reduce GHGs; it can legislate to accomplish much of what the Act aims to do.
 The provinces, too, have significant lawmaking authority that allows them to reduce GHGs. In a federal constitutional order, a variety of different approaches may be taken to the same problem, with each jurisdiction learning from the experience of the others. That is how Canada has long been governed. As the Supreme Court has emphasized, Canadian federalism is characterized by overlapping legislative jurisdiction and cooperation to achieve national goals. Canada has not established that Parliament’s lawmaking authority should be expanded under the POGG power in this case.
The Ontario government has indicated it will seek leave to appeal the decision to the Supreme Court of Canada.