The Trans Mountain pipeline expansion is headed back to court, with the Raincoast Conservation Foundation and the Living Oceans Society asking an appeal court to rule that the federal cabinet failed to protect British Columbia’s endangered southern resident orca population when it re-approved the controversial, C$9.3-billion project.

“This case is about whether the government has the power to justify pushing an endangered species closer toward extinction, which we say is a matter that really needs to be settled by the court,” said Margot Venton, nature program director at Ecojustice, which filed the suit Monday on behalf of the two non-profits.

“The groups are asking for leave to appeal the pipeline expansion approval, marking the second time they’ve gone to court over the issue,” CBC reports. “Just 76 killer whales remain in the southern resident population, and environmentalists argue an increase in tanker traffic connected to the pipeline expansion, as well as the danger of an oil spill, would put the animals at greater risk of extinction.”

The National Energy Board acknowledged as much last year, in a report that suggested the whales would face “significant adverse effects” due to the pipeline expansion.

“Venton said the conservation organizations are also concerned about the rise in carbon dioxide emissions that will follow the pipeline’s expansion, including the emissions that will come from extracting the oil from Alberta’s oilsands, transporting it, and burning the fuel overseas,” CBC adds. “The Tsleil-Waututh Nation has also indicated it will file an appeal of the June 18 cabinet approval.”