“It is ridiculous to assert that B.C.’s opposition amounts to a regional blockade against a project ‘in the national interest.’ No province should act unreasonably to block neighbour – or national – priorities. But federalism doesn’t mean that one province gets to tread on the rights and threaten the environment of another,” wrote Mr. Weaver, who in 2013 became the first Green elected to B.C.’s legislature.  “It means we work together to assess and advance the national interest.”

The feds haven't tread on BC's rights here, nor will the pipeline threaten the environment.  Last time I checked there were several million kilometers of pipelines in North America.  And the environment seems to be in pretty good shape.  

The last sentence is key to the issue and is why pipelines are in the federal jurisdiction.