A Canadian court on Thursday froze plans to expand an oil pipeline that the government is about to purchase, ruling that the government’s National Energy Board had not adequately consulted with Indigenous people along the pipeline’s route or assessed the project’s potential effects on the waters off British Columbia... While the practical effect of the decision may be a comparatively short construction delay, the ruling added fuel to an already incendiary debate over the Trans Mountain pipeline... After the pipeline’s owner, Kinder Morgan of Houston, abandoned its plans to add a second pipeline along the existing Trans Mountain route in April, Prime Minister Justin Trudeau’s government stepped in to buy [the pipeline]... Environmentalists and some Indigenous groups immediately called the ruling a major victory, and some of them urged Mr. Trudeau’s government to give up on plans for the expansion... Mr. Trudeau’s backing of the pipeline... was to some degree a move to persuade Alberta to join his national carbon-tax program. Alberta’s energy industry, particularly the oil sands, is a major carbon emitter, making the province’s cooperation vital... Rachel Notley, the province’s premier, said that Alberta was withdrawing from the carbon-tax program until construction began on the Trans Mountain extension... The court said that the new set of consultations it had ordered would most likely be “brief and efficient while ensuring it is meaningful,” making for “a short delay” in the pipeline project.