Michigan Supreme Court Orders New Environmental Review for Controversial Great Lakes Pipeline Tunnel

2026-08-02 companies

Lansing, Saturday, 1 August 2026.
The Michigan Supreme Court ruled 6-1 that state regulators must reconsider Enbridge’s Line 5 tunnel permit, citing ignored environmental risks and threats to Indigenous treaty rights in the Great Lakes.

Supreme Court Mandates Permit Review

On July 31, 2026, the Michigan Supreme Court issued a 6-1 ruling ordering state regulators to reconsider the permit for Enbridge Inc.’s proposed tunnel project under the Straits of Mackinac [1]. The decision cites a failure to evaluate the project’s impact on the pipeline’s lifespan, environmental harm, public trust rights, and alternatives like rail or truck transport [1]. This ruling creates renewed legal and regulatory uncertainty for the Calgary-based energy infrastructure giant’s controversial Line 5 pipeline [1]. Business leaders and energy sector analysts are closely monitoring the legal battle, as potential delays or shutdowns could significantly impact Midwest refinery capacity and broader North American cross-border energy trade [1]. The Court determined that the Michigan Public Service Commission violated the Michigan Environmental Protection Act and public trust doctrine when approving the 2023 tunnel permit [3].

Pipeline Infrastructure and Capacity

Enbridge’s Line 5 pipeline was constructed in 1953 and spans 645 miles from Superior, Wisconsin, through Michigan to Sarnia, Ontario [2]. The system includes a 6-kilometre section running along the bottom of the Straits of Mackinac between Lake Michigan and Lake Huron [1]. Line 5 currently transports over 500,000 barrels of oil daily through the Great Lakes, with some reports indicating capacity up to 540,000 barrels per day [1][3]. In gallon terms, 540,000 barrels equates to approximately 22.680 million gallons of crude oil and natural gas liquids daily [GPT]. The pipeline system operates under a 1953 easement granted to Lakehead Pipe Line Company, a predecessor to Enbridge [4]. Enbridge proposed the tunnel project nearly a decade ago, around the time a ship anchor dented the existing pipeline [1].

Legal and Regulatory Timeline

On November 13, 2020, Michigan Governor Gretchen Whitmer and state officials revoked the 1953 easement, requiring decommissioning by May 2021 [3]. Despite this, the Michigan Public Service Commission originally approved the tunnel permit in 2023, which was subsequently challenged in a lawsuit by four Michigan tribal nations and various environmental groups [1]. On January 14, 2025, the Michigan Court of Appeals heard arguments regarding the MPSC permit, subsequently upholding it in February 2025 [3]. On April 2, 2025, four Tribal Nations, alongside the Michigan Climate Action Network and Environmental Law & Policy Center, filed an appeal with the Michigan Supreme Court to overturn the Court of Appeals decision [3]. Additionally, on April 22, 2026, the U.S. Supreme Court unanimously ruled that Michigan Attorney General Dana Nessel’s Line 5 lawsuit belongs in state court [6]. Enbridge is currently reviewing legal options following the recent court ruling that delays the pipeline tunnel project [1].

Environmental and Tribal Implications

Enbridge’s Line 5 has leaked at least 33 times, discharging over 1.1 million gallons of oil to date [3]. Investigations indicate that most historical spills were not identified by Enbridge’s leak detection systems [2]. The Bay Mills Indian Community, supported by the Native American Rights Fund, opposes the proposed tunnel project, citing threats to sacred waters, treaty rights, and economic reliance on local fishing and hunting [3]. Opponents argue that the tunnel construction would take 10 years to complete, leaving the Straits vulnerable to pipeline rupture during that period [2]. David Gover, an attorney with the Native American Rights Fund, stated that whether Line 5 is suspended in the water or encased in a tunnel, it is simply a terrible idea to pump more than half a million barrels of oil every day through the middle of the Great Lakes [1]. The Native American Rights Fund intends to present arguments defending Tribal rights and Great Lakes protection during the upcoming MPSC permit review proceedings [3].

Sources

Enbridge Pipeline Regulation