Two hereditary chiefs from a British Columbia First Nation at the heart of a wave of national protests launched a constitutional challenge of fossil fuel projects on Wednesday as Prime Minister Justin Trudeau called for demonstrators to observe the rule of law.

The challenge calls on the Federal Court to declare that Canada is constitutionally obliged to meet international climate change targets, which the chiefs contend would cancel approvals for a natural gas pipeline that runs through traditional Wet'suwet'en territory in northern B.C.

"If Canada is allowed to continue approving infrastructure for fracked gas projects on a 40-year timeline, our territories will become a wasteland before the project licenses expire," Chief Lho'imggin, who also goes by Alphonse Gagnon, said in a statement.

"As house chief it is my responsibility to protect our house territory. We're asking the court to get Canada to act before it is too late."

The challenge came as protesters continued to blockade major ports and rail lines in Ontario, Quebec and British Columbia, scuttling freight and passenger service and prompting growing calls for federal government intervention.

Speaking in Senegal on Wednesday, Trudeau called on all sides to resolve their differences but insisted that protesters must honour Canadian law.

"We recognize the important democratic right -- and will always defend it -- of peaceful protest," Trudeau said during a news conference with Senegal President Macky Sall. "But we are also a country of the rule of law, and we need to make sure those laws are respected."

Trudeau's remarks, echoed by Canada's transportation and finance ministers throughout the day, drew scorn from Indigenous protesters backing the Wet'suet'en hereditary chiefs.

Herb Varley, who helped organize a blockade at the Port of Vancouver, accused Trudeau of "mindlessly parroting" the term rule of law, which he said is empty rhetoric.

If his elders had followed the rule of law, he said their language would have died out.

"If my Nisga'a grandmothers, grandfathers, aunties and uncles had followed the rule of law, we wouldn't know we were Nisga'a," he said outside the B.C. Supreme Court in Vancouver, where he and other protesters announced they were challenging an injunction served against them over the weekend.

Blockade organizers across Canada have said they're acting in solidarity with those opposed to the Coastal GasLink pipeline project that crosses the traditional territory of the Wet'suwet'en First Nation near Houston, B.C.

The blockades were erected after the RCMP enforced a court injunction last week against Wet'suwet'en hereditary chiefs and their supporters, who had been blocking construction of the pipeline, a key part of a $40-billion LNG Canada liquefied natural gas export project.

Another group of supporters took to the streets in Ottawa on Wednesday morning, moving from the office of the federal justice minister into a major intersection near the Supreme Court of Canada. The crowd caused a traffic jam that backed up vehicles for blocks, but the delay was cleared in less than an hour as protesters dispersed.

Similar protests in Vancouver tied up traffic at different points of the city throughout the day.

B.C. Premier John Horgan said anti-pipeline demonstrators who prevented people from entering the legislature for his government's throne speech on Tuesday need to respect the rights of others.

"Peaceful demonstration is fundamental to our success as a democracy," he told a news conference in Victoria on Wednesday. "But to have a group of people say to others you are illegitimate, you are not allowed in here, you are somehow a sellout to the values of Canadians is just plain wrong, and I want to underline that."

The economic impact of the demonstrations has started to crystallize: Canadian National Railway Co. warned Tuesday that it would have to close "significant" parts of its network unless blockades on its rail lines were removed.

Passenger rail services have also been affected in Ontario, Quebec and B.C., with Via Rail cancelling service on its Montreal-Toronto and Ottawa-Toronto routes until at least the end of the day on Friday because of a blockade near Belleville, Ont. It had previously cancelled service on those routes until the end of the day on Thursday.

Via has also said a blockade near New Hazelton, B.C., means normal rail service is being interrupted between Prince Rupert and Prince George.

In Manitoba, Premier Brian Pallister said the Justice Department will seek an injunction to end a rail blockade west of Winnipeg and have it enforced within a few days.

"As much as we will always respect the right of protesters to have a voice, they don't have a veto and ... they don't have the right to put their rights ahead of everyone else and to disregard the laws of our province and country," he said in an interview.

The Alberta wheat and barley commissions said rail disruptions of just a few days will cause economic loss for farmers, who have faced difficult harvest conditions.

"Delays will result in farmers being unable to deliver their grain, meaning they can't be paid at least until service resumes," said Dave Bishop, chair of the barley commission. "We are still recovering from the harvest from hell and need reliable grain movement in order to get back on track."

Mohawks at a barricade that has disrupted rail traffic near Montreal said they'll remain in place as long as the RCMP is present on Wet'suwet'en territory.

Tekarontake, a Kahnawake Mohawk, said the conflict is the result of a failure by governments and others to accept that the land belongs to the people who continue to adhere to the ways of their ancestors.

"That's whose land this is, we have never disconnected ourselves from our mother. This land is our mother," he said. "We haven't abandoned her, we still love her, we care for her and we will defend her to the best of our ability."

Natural Resources Minister Seamus O'Regan said Transport Minister Marc Garneau is "seized" with the blockades affecting railways.

"Our economy really relies on our ability to safely transport goods across the country," he said.

Asked how he could assure industry that natural resource projects can proceed in Canada, O'Regan said there will always be differing opinions.

"As we work toward net zero (emissions) by 2050 and considering we are an economy that relies heavily on natural resources and natural resource development, there's always going to be that friction. There will always be that tension."

This report by The Canadian Press was first published Feb. 12, 2020.