Army Corps Issues Line 5 Tunnel Permit While Michigan's 6-1 Court Ruling Still Blocks It

The Situation

Great Lakes propane supply planners got a federal green light for Line 5's replacement tunnel this summer, and still no construction date. The U.S. Army Corps of Engineers issued Enbridge the federal permit it needs to bore beneath the Straits of Mackinac on Aug. 12, 2026. Detroit District officials signed off after a review covering the Clean Water Act, the Endangered Species Act, and federal Tribal trust obligations. But the federal approval doesn't clear the way to construction: weeks earlier, the Michigan Supreme Court ruled 6-1 that state regulators skipped required environmental analysis, unwinding the project's state permit. For anyone tracking Great Lakes supply lines that carry natural gas liquids, the pipeline's legal status stays unsettled even with Washington's review finished.

The Facts

USACE's Detroit District issued Enbridge Energy an individual permit for work in federally regulated waters at the Straits of Mackinac on Aug. 12, 2026. The project bores a tunnel through roughly four miles of lakebed, the Corps says, to house a replacement segment of the existing Line 5 pipeline, and the agency's Record of Decision covers reviews required under the National Environmental Policy Act, the Clean Water Act, the Rivers and Harbors Act, the Endangered Species Act, the National Historic Preservation Act, and federal Tribal trust responsibilities. The record shows the project is not contrary to the public interest and doesn't impermissibly impair Tribal treaty rights, per Michigan Public.

Detroit District Commander Lt. Col. Donald K. Lew called it 'a very carefully weighed decision' shaped by input from federal and state agencies, tribes, and Enbridge.

Enbridge itself called the approval 'a significant step forward' reflecting 'more than six years of rigorous, comprehensive review,' the company said in a statement. That federal clearance follows a setback in state court. Weeks earlier, the Michigan Supreme Court ruled 6-1 that the Michigan's Public Service Commission (MPSC) failed to fully evaluate the tunnel's environmental impacts when it approved the project, according to WDIV.

The ruling came less than two weeks after Michigan's Department of Environment, Great Lakes, and Energy (EGLE) and the Department of Natural Resources (DNR) had issued their own environmental permits, per WDIV. The high court's decision sends the matter back to the MPSC for further review before construction can proceed — a point Bay Mills Indian Community President Whitney Gravelle raised in comments to WDIV. Meanwhile, Attorney General Dana Nessel's separate lawsuit seeking to shut down Line 5 over alleged public trust doctrine and Michigan Environmental Protection Act violations remains pending.

Enbridge is countersuing, arguing the state's claims are preempted by the federal Pipeline Safety Act, and Canada has told Michigan it's violating a bilateral treaty over the pipeline, per Michigan Public. The environmental group Oil and Water Don't Mix called the decision 'a thoroughly flawed product of a rushed process driven by the Trump Administration's phony national energy emergency' in its own statement. Line 5 carries light crude oil and natural gas liquids across 645 miles from Superior, Wisconsin, to Sarnia, Ontario, crossing the Straits over roughly 3.7 miles at depths up to 240 feet, where a single 30-inch pipeline splits into two 20-inch lines, according to USACE.

NGLs are the same feedstock family that includes propane, though none of the sources break out how much propane specifically moves through the line. A firm construction start date is not yet confirmed — it depends on how fast the MPSC completes its court-ordered review and how the Nessel lawsuit and Enbridge's countersuit resolve.

Business Impact

Nothing about this permit gets a shovel in the ground yet. The tunnel would replace the aging Straits segment that also carries the natural gas liquids that eventually reach propane markets around the Great Lakes, so its legal status is worth tracking even without a construction date on the calendar. The Corps' approval settles the federal side of a permitting fight Enbridge said took more than six years, but the state side just reopened, and two separate lawsuits over the existing pipeline's future are still working through the courts.

What this means for your business: 1. With the Army Corps' review done, Line 5's timeline now runs through Michigan courts. 2.

The MPSC's court-ordered reevaluation adds a state-level checkpoint with no announced schedule, so any tunnel-completion assumption in supply planning needs a wide error bar. 3. Nessel's shutdown suit, if it succeeds, would hit the existing Line 5 segment, not just the future tunnel — a bigger near-term risk to Great Lakes NGL logistics than the permitting fight itself.

1. 1.Enbridge's federal-preemption defense and Canada's treaty complaint could push this dispute beyond Michigan courts entirely, adding more time before any resolution.

Key Takeaways

• The federal permit finishes the Army Corps' review, but it doesn't authorize construction because the tunnel's state approval was thrown out by the Michigan Supreme Court.
• The 6-1 ruling sends the project back to the Michigan's Public Service Commission for a fuller environmental evaluation with no confirmed timeline.
• AG Dana Nessel's shutdown lawsuit and Enbridge's countersuit over federal preemption remain unresolved and could outlast the tunnel permitting fight.
• Line 5 moves natural gas liquids alongside light crude, so its legal limbo is worth watching even though the sources don't specify propane volumes.

Action Steps

1. 1.Pull the Army Corps' Record of Decision this week to see the specific conditions attached to the federal permit.
2. 2.Check the Michigan's Public Service Commission's docket for movement on its court-ordered reevaluation before assuming a construction start date.
3. 3.Track AG Nessel's public trust doctrine lawsuit and Enbridge's federal-preemption countersuit for a ruling that could affect the existing pipeline sooner than the tunnel timeline does.
4. 4.Flag any Line 5-linked NGL or propane supply contracts for a status review at your next planning meeting, since no construction start date has been set.

Competitive Advantage

Marketers who treat Line 5's future as unresolved can hedge Great Lakes NGL exposure earlier than competitors banking on a quick construction start. Watching the MPSC docket and the Nessel suit directly, rather than waiting for tunnel headlines, gives operators a longer runway to line up alternate supply if either case breaks against Enbridge.