While saying that policy decisions were best left to legislators to decide, the court still found the law was valid based in part by experts claiming a price on carbon was the best method to fight climate change.
However, before Canada's highest court hears these arguments, Moe said Canadians "have an opportunity to decide the fate of the damaging and ineffective Trudeau carbon tax during the federal election this October". The act became a sound response to potentially catastrophic climate change, federal attorneys argued.
Ontario's position was that there didn't need to be a carbon tax, or price if you prefer, in order to reduce greenhouse gas emissions. "They are regulatory in nature and connected to the purposes of the act". However the province of British Columbia has had a carbon tax for years and it has reduced emissions and the economy is doing very well.
Nathalie Chalifour, an associate professor of law at the University of Ottawa, said the two Court of Appeal rulings show if the matter was appealed to the Supreme Court, "chances are nearly certain it will be upheld again".
In a dissenting blueprint, Justice Grant Huscroft said climate change did no longer quantity to an "emergency case" and warned in opposition to permitting rhetoric to coloration the constitutional evaluation. Carbon pricing is only one way to deal with greenhouse gases, he said. "There are a ramification of systems to address climate change and the provinces occupy big authority to pursue them".
It has similarly imposed the tax on the provinces of New Brunswick, Saskatchewan and Manitoba, and plans to do the same on January 1, 2020 in the province of Alberta. Alberta is in the process of its own challenge against the law.
Friday's decision marks the second consecutive legal setback for opponents of Ottawa's carbon tax system.
Saskatchewan's top court also upheld the federal legislation in May, and the provincial government is appealing.
Federal Environment Minister Catherine McKenna called the judgment good news for Canadians who believe climate action is urgent.
In all, 14 interveners - amongst them some provinces, Indigenous groups and environmental and industrial organizations - lined as a lot as shield or attack the legislation, with most siding with Ottawa.
Some observers said the Ontario challenge was more about politics than the environment.
The issue is expected to be ultimately decided by the country's top court.
In a joint statement, Ontario Premier Doug Ford and Environment, Conservation and Parks Minister Jeff Yurek said the province was "disappointed" with the ruling and would appeal to the Supreme Court of Canada.
It also agreed that modifying the behaviour of Canadians was a objective of the legislation and said the charges in the act are "not required to be cost recovery mechanisms", as Ontario suggested. Environment Minister Catherine McKenna says Albertans will face a federal carbon price on January 1, after the move by Premier Jason Kenney to kill the system imposed by the previous NDP government.
Ontario Green Leader Mike Schreiner said he was relieved the courts rejected Ford's attempts to make Ontario a "rogue actor in the fight against the climate crisis" while New Democrat Peter Tabuns said the challenge was a "political stunt" aimed at helping the federal Conservatives in the coming election.