Photo: The Canadian Press. All rights reserved.

A group of protesters gathers outside the Northern Gateway hearings in Prince Rupert, B.C. Monday, December, 10, 2012. THE CANADIAN PRESS/Jonathan Hayward

There have been times over the past few days at the review hearings into the proposed Northern Gateway pipeline when the testy exchanges between Enbridge experts and First Nations lawyers have bordered on verbal warfare.

And as the project moves further toward an environmental assessment decision, it seems increasingly likely that the debate about the oil pipeline, an oil pipeline, any oil pipeline, will end in a showdown between the federal government and First Nations over aboriginal rights.

"I think on the First Nations side, there's no question they're marshalling resources to go to court," said Gordon Christie, director of indigenous legal studies in the University of British Columbia's faculty of law.

As lawyers for the Haisla Nation questioned company experts under oath in the conference room of a casino in Prince Rupert on Thursday, 1,500 kilometres south in Vancouver, the Tahltan Nation and the B.C. Metis Federation announced that they have added their names to a petition banning oil pipelines and tankers from traditional territories.

Now, the proposed Northern Gateway pipeline route doesn't actually enter Tahltan territory around Stewart, B.C., and the B.C. Metis Federation does not have traditional lands.

But Chief Martin Louie of the Nadleh Whu'ten First Nation said the addition of the two groups shows pipeline opposition is gaining momentum.

"Whether in the north or the south, we are all threatened and we are all connected," the Yinka Dene said in a letter inviting the Metis to join their campaign opposing the Northern Gateway and Trans Mountain pipeline projects.

The petition launched by the Yinka-Dene two years ago now has more than 130 bands on board. The alliance would ban pipelines and tankers in the Fraser River watershed. It would also stop oil tankers in the ocean migration routes of Fraser River salmon all along coastal British Columbia.

Petition organizers say signatory First Nations form an unbroken chain that spans the entire length of the province.

Unlike other provinces, First Nations in B.C. did not sign treaties with the colonial government, and decades of modern-day treaty negotiations have largely failed.

"We know they have aboriginal rights. We just don't know what they are," Christie said. "There hasn't been a treaty or any court cases to set out what they are."

The courts have ruled that the Crown has a duty to consult aboriginal groups, but whether it has a duty to gain the consent of aboriginal groups is unclear. Certainly, several of the B.C. bands opposing the Northern Gateway project see it that way.