Rochdale68,

It's not ambiguous under Canada's Constitution that the Federal Government can press ahead with clearing away BC Government measures to block the twinning of Kinder Morgan & export of diluted bitumen through the Salish Sea.  However, to remove all doubt against determined efforts by a BC Government, the Federal Government would have to declare the pipeline expansion to be a project in the national interest under a Constitutional provision that hasn't been invoked for 8 decades.

Provincial Governments generally would be upset by such a blast from the past. However, most are equally put off by the blockages & rent-extraction that BC Governments have recently threatened for transshipment of goods from other Provinces through BC.

All these tests of the creaky customs union aspects of Canada's Constitution are unwelcome at a time that NAFTA & other trade arrangements are under a cloud.