Chief Na’Moks stood in the dark of a small smokehouse nestled in the Coast range of British Columbia. Hanging above him were nearly a thousand fish which glinted over the fire below.

“For us, it’s one of the most highly prized commodities that we have,” he said, pulling one of the glistening candlefish off the rack. “People don’t get why we want to keep what we have. We don’t want anything from anyone. We just want to keep what we have.”

Not so long ago, the chief’s ancestors traded fish oil along the grease trails up and down the coast of British Columbia. Today, however, Chief Na’Moks and many other First Nations leaders are at the forefront of a struggle against a very different kind of oil business: Canada’s largest proposed tar sands pipeline, the Northern Gateway.

It is the country’s environmental battle of the decade, uniting a wide variety of citizens’ groups against the billions of dollars of investment by oil companies and millions in secret funding from the government. First proposed in 2004, the Enbridge Northern Gateway pipeline was planned for a 731-mile (1,177km) stretch from the center of Alberta to the coast of British Columbia.

The plan was to carry diluted bitumen from the tar sands, across hundreds of waterways, over two major mountain ranges and through some of the wildest country in North America. It was approved, with 209 conditions, in June of 2014.

Environmental groups, citizen activists and First Nations have used everything from lawsuits to old-fashioned civil disobedience to battle the project – and so far they have been successful. No mean feat, considering that Canadian prime minister Stephen Harper took office in 2006 pledging to make the country into an “energy superpower”.

Seeking a fourth term in office in federal elections on Monday, Harper’s Conservative party has been decidedly quiet the subject of fossil fuels. Last year’s crash in oil prices and Harper’s failure to build the Keystone XL pipeline have both sent tremors through the country’s fossil-fuel industries.

Then in May, the upstart New Democratic Party won a stunning victory in Alberta’s provincial elections, ending 44 years of Conservative rule.

The Northern Gateway played a crucial role in that election: Alberta’s former premier Jim Prentice had previously been employed by the pipeline company Enbridge to make peace with First Nations opposed to the the pipeline. As premier, he tried to get First Nations to agree to pipelines by offering them a share in the profits.

The leaders of the two largest opposition parties – the New Democratic Party and the Liberals – have vowed far greater oversight of the oil industry. NDP leader Tom Mulcair has said the approval process for pipelines is “singularly defective”. And Liberal leader Justin Trudeau said it was “not for governments to be cheerleaders for various pipelines”.

Even as the political battles rage, the Northern Gateway is back in court for a new round that may prove decisive. A group of First Nations, environmental organizations and a labor union argued that the approval process for the pipeline was flawed, did not take environmental impact into account and violated the rights of First Nations. It was the longest case ever heard before the federal court of appeals, Canada’s second-highest federal court.

The Haisla are one of eight First Nations taking part in the case. When Gerald Amos, whose Haisla name is Gagamguist, was asked what the Conservative government could do to work better with First nations, he simply responded: “The best thing that can happen with the conservative government is to be un-elected.”

Amos was sitting on the beach in Kitimat Village, the traditional fishing village of his people that sits on an inlet of Douglas Channel. He spoke slowly, weighing his words. “The only good thing that’s come out of Enbridge is it has brought us together,” he said.

He was speaking about the First Nations village and the industry town supporting an aluminum smelter that largely joined forces for the Enbridge fight. As Canada’s election approaches, the race remains too close to call. Many people will be voting based on the politics and economics of oil, pipelines and the environment.

“Canada has to remind themselves of who they are,” said Chief Na’Moks. “I believe that all Canadians should vote, and vote properly – vote for your future, not just for words.”