The British Columbia (BC) government lost its final legal appeal Thursday to stop the Trans Mountain Pipeline expansion (TMX) as a growth enabler for Canada's top natural gas user, Alberta thermal oil sands production.

After a day of lawyer arguments in Ottawa the Supreme Court of Canada unanimously upheld a May 2019 verdict against provincial interference with the project by the BC Court of Appeal, which was also unanimous.

The courts ruled that Canada's constitutional division of powers prevents BC's New Democratic Party (NDP) administration, a declared TMX opponent, from usurping federal jurisdiction over a national enterprise.

The failed NDP maneuver was a legislative proposal, billed as environmental protection against oil spills, for BC power to inflict penalties of up to C$400,000 ($300,000) and six months in jail for increasing bitumen shipments via TMX.

The Alberta government, a stalwart Trans Mountain supporter, showered praise on the favorable verdict. Provincial Justice Minister Doug Schweitzer predicted, "Building the TMX and ensuring a fair price for our natural resources will create thousands of new jobs and increased prosperity that will benefit the entire country."

Construction has begun on Trans Mountain's Vancouver Harbor outlet and Edmonton inlet on facilities to triple capacity to 890,000 b/d on the 987-kilometer (592-mile) pipeline across Alberta and BC.

Work will start on other sections as TMX finishes a laborious final regulatory procedure: detailed route review of construction locations, timing and methods on about 3,000 properties crossed by the pipeline.

Hearings are under way on landowner and native objections with potential to require expensive construction changes. Detailed route review results will figure in the final cost for TMX, which is currently forecast to hit about C$9 billion ($6.8 billion).

The legal chapters in the six-year TMX regulatory ordeal also remain unfinished. A verdict is awaited on a protest lawsuit by four native tribes, calling for the Canadian Federal Court of Appeal to overturn the project's national approval.

Ownership change is also on the project's horizon. Since buying TMX from its original sponsor, Texas-based Kinder Morgan, for C$4.5 billion ($3.4 billion) in 2018, Canada's federal government has lined up native bidders for shares in the oil export conduit after completion of the capacity expansion.