In a landmark decision, Canada’s Supreme Court has ruled against one of Justin Trudeau’s keystone environmental laws. The court found that Bill C-69, known as the Impact Assessment Act, is largely unconstitutional, dealing a blow to federal efforts to regulate Alberta’s oil and gas projects.

The Supreme Court had been tasked with determining whether the Impact Assessment Act and its regulations exceeded Parliament’s legislative authority under the Constitution. The Act establishes a complex two-part regulatory scheme. One part sets up an impact assessment process for federal projects, and the second part designates which projects are automatically subject to federal review.

Many accused the Trudeau Government of designing the act specifically impede Alberta’s oil and gas sector.

Last year, Alberta’s government referred two constitutional questions about Trudeau’s scheme to the Alberta Court of Appeal. The Alberta Court found the Act and its regulations to be unconstitutional in their entirety.

The Attorney General of Canada appealed this decision to the Supreme Court. Unlike the federal government, provincial governments must first direct their questions to their courts of appeal, but these can then be appealed to the Supreme Court without requiring permission.

The Supreme Court allowed the appeal only in part. While sections 81 to 91 of the Act were found to be constitutional, the majority of the scheme was deemed unconstitutional.

Chief Justice Wagner, writing for the majority, stated that the scheme is unconstitutional in part for two overarching reasons. First, it does not focus on regulating “effects within federal jurisdiction” as defined in the Act. Second, the term “effects within federal jurisdiction” does not align with federal legislative jurisdiction.

“[Environmental protection remains one of today’s most pressing challenges. However,] Parliament also has the duty, however, to act within the enduring division of powers framework laid out in the Constitution,” Chief Justice Wagner wrote.

Remarkably, nine out of ten provinces are opposed to the federal government’s Bill C-69.

Conservative leader Pierre Poilievre opposes Bill C-69. Last year, he pledged to abolish the bill and eliminate overseas oil imports within five years.