Opponents of the Trans Mountain pipeline expansion are preparing for a long summer of legal challenges and protests aimed at blocking the project from being built.

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

Squamish Nation Coun. Khelsilem says his band is also prepared for legal action and Vancouver Mayor Kennedy Stewart says the city will join any lawsuits that are filed.

Lawyer Eugene Kung says there are a number of legal arguments opponents could advance, including that it was impossible for the federal government to make an unbiased decision as the owner of the pipeline.

But Eric Adams, a law professor at the University of Alberta, says the court may be uncomfortable setting a precedent that governments cannot approve projects they support.

A 20-kilometre march is planned for Sunday from Victoria to the Saanich peninsula in solidarity with First Nations that are opposed to the project.