VANCOUVER - Opponents of the Trans Mountain pipeline expansion are preparing for a long summer of legal challenges and protests aimed at blocking construction of the project.

Rueben George of the Tsleil-Waututh Nation said it will file a legal challenge in the Federal Court of Appeal and he is certain it will be successful after Ottawa approved the project on Tuesday.

“I'm not even worried,” he said. “I've never felt more confident in what we have to bring victory to us. We will win again.”

The First Nation in North Vancouver, B.C., was among the Indigenous groups, environmental organizations and cities that won a legal challenge in the Federal Court of Appeal last August. The court struck down the project's approval, citing the National Energy Board's inadequate Indigenous consultation and failure to consider marine impacts.

After a second energy board review, the federal cabinet approved the project again.

Khelsilem, an elected Squamish Nation councillor, said his band will also file a legal challenge. It will argue the consultation was “shallow” because it was rushed to meet an arbitrary deadline, he said.

“Constantly, we were being told, 'We have to get your response by this date, and we have to get this report in by this date, because cabinet's making a decision in June,' ” he said.

“The actual substance that we were able to get into was completely undermined by the government's own self-imposed deadline.”

Vancouver Mayor Kennedy Stewart said Tuesday the city will join any legal challenges that are filed. British Columbia Premier John Horgan said he'd first have to look at the applications, but if it was in B.C.'s best interest to join, it would.

Chief Leah George-Wilson of the Tsleil-Waututh said the nation will also argue in court that the consultation was not meaningful. The government has not addressed any of the nation's concerns about the way diluted bitumen responds in water or how much noise southern resident killer whales can tolerate, she said.

“It fell short because they had a limited mandate and a compressed timeline, and they weren't really able to address any of our issues,” she said.

The government tasked former Supreme Court justice Frank Iacobucci with overseeing the latest round of consultations. It said Tuesday it had made several accommodations to address Indigenous concerns, including a long-term investment strategy to help First Nations monitor southern residents.

It also said it had amended six conditions imposed upon the project, including to increase Indigenous participation in marine response plans and monitoring activities during construction.

George-Wilson said the Tsleil-Waututh has always participated in spill response and the accommodations don't address its concerns about the shortcomings of the federal government's response capacity.

Eugene Kung, a lawyer with West Coast Environmental Law, said there are a number of legal arguments opponents could advance, including that the Trudeau government's $4.5-billion purchase of the project put it in a conflict of interest.

“It doesn't take a rocket scientist to figure out that when they bought the pipeline, it made it a lot harder to make an unbiased, open-minded decision,” he said.

It appeared the minds of federal cabinet members were already made up before the latest round of consultations, reducing the process to a note-taking exercise rather than a meaningful conversation, Kung said.

Kung added that the government is not only the decision-maker and proponent, it's also in charge of enforcing laws such as the Species At Risk Act, prosecuting a spill if one occurs, and acting in trust for First Nations whose territories are crossed by the pipeline.

Eric Adams, a law professor at the University of Alberta, said the conflict of interest argument is a “novel and creative” way to attack the federal government's actions, but he doubts it will hold water in court.

“I suspect a court will be concerned with the logical extension of that chain of reasoning, which is that any time the government is an owner or part owner of infrastructure, by definition it's incapable of consulting in good faith,” he said.

Opponents are also planning protests, including a 20-kilometre march on Saturday from Victoria to the Saanich peninsula. Marchers will lead a tiny house along the route in solidarity with First Nations who have built small homes on the pipeline path in B.C.'s Interior.

Will George, a Tsleil-Waututh man who rappelled from Vancouver's Ironworkers Memorial Bridge to protest the project last year, promised more “direct action” at a rally that drew hundreds on Tuesday night.

“When I choose to go hang off another bridge, I need you guys here,” he told the crowd. “There are three more bridges, right? So we got options.”