CALGARY, Alberta—The government of British Columbia will not allow Kinder Morgan Canada Ltd. to begin work on public land for its Trans Mountain pipeline expansion until it “meaningfully” consults aboriginal communities, the Canadian province’s environment minister said on Aug. 10.

Minister George Heyman told reporters in Vancouver that the government will seek intervener status in court cases against federal approval of the project. Heyman said the company needs to meet standards laid out by Canadian law, without specifying the benchmark for consultation to which Kinder Morgan would be held.

“We know with the federal government’s approval of this project, the path forward will be challenging, but we are committed to stepping up and fighting for B.C.’s interests,” he said. “We will continue to explore every tool possible.”

“We are committed to working with the Province and permitting authorities in our ongoing process of seeking and obtaining necessary permits and permissions,” Ian Anderson, President of Kinder Morgan Canada, said in a statement. “We have undertaken thorough, extensive and meaningful consultations with Aboriginal Peoples, communities and individuals and remain dedicated to those efforts and relationships as we move forward with construction activities in September.”

Shares in Kinder Morgan Canada fell as much as 5.7% shortly after the minister’s comments, while shares in Houston-based parent Kinder Morgan Inc. (NYSE: KMI) dropped as much as 2.0%.

The prospect of Kinder Morgan Canada’s project has become more uncertain since the Green Party-backed alliance came to power in British Columbia in June and vowed to use “every tool” to fight the expansion.

The project would almost triple the capacity of the current Trans Mountain pipeline to the West Coast. Canadian crude producers, whose landlocked product trades at a discount, say they need the expansion to access new markets and command better prices.

The expansion has federal approval, but faces opposition from British Columbia’s ruling left-leaning New Democratic Party (NDP) and the environmentalist Green Party that props it up.

The parties, who together form a legislative majority, ousted the pro-business Liberal government in June after a cliffhanger election in May.