EPA Backs Enbridge's Line 5 Tunnel as Two States Push Back

The Trump administration's Environmental Protection Agency has come out in support of Enbridge's proposed Line 5 tunnel beneath the Straits of Mackinac, even as Michigan and Wisconsin continue applying legal and regulatory pressure to the crude oil pipeline, with Enbridge (ENB) shares trading at 46.48, down 1.04%, at 18:45 GMT on Sept. 29, 2026.

A single stretch of pipe running under the Straits of Mackinac has become the clearest test yet of what happens when federal energy policy and state environmental authority point in opposite directions. The Environmental Protection Agency under President Trump has thrown its weight behind Enbridge's plan to encase Line 5 in a tunnel beneath the straits, while Michigan and Wisconsin continue to press the company from the other direction.

Enbridge (ENB) was trading at 46.48 at 18:45 GMT on Sept. 29, 2026, down 1.04% on the day from a previous close of 46.97, with a session range of 46.38 to 46.91. That is a steeper decline than the broad market: the S&P 500 tracker (NYSEARCA: SPY) was off 0.09% at $764.91 and the Dow 30 tracker (NYSEARCA: DIA) down 0.25% at $512.75, while the Nasdaq 100 tracker (NASDAQ: QQQ) was up 0.28% at $738.57.

Two Governments, One Pipe

Line 5 sits in an unusual position in North American energy infrastructure. It is a cross-border line, feeding refineries on both sides of the border, and it crosses state land and water where the permitting authority does not belong to Washington. That split is the whole story. Federal support for the tunnel project does not, by itself, clear the way; state permits, state court actions and state attorneys general each have their own levers, and Michigan and Wisconsin have been using them.

The tunnel proposal is Enbridge's answer to the central objection raised against the line: that a rupture in open water at the straits would be an environmental event of a scale no operator could contain quickly. Burying the crossing in a bored tunnel is meant to take that scenario off the table. Opponents argue it entrenches a line they want retired outright, and prolongs the asset's life by decades rather than winding it down.

What the EPA's backing changes is the political weather around the project rather than the legal mechanics. As Forbes Business reported, the federal position now runs squarely against the two state governments most determined to constrain the line, with energy security arguments being made on the federal side.

Why the Refining Map Matters Here

The energy security argument is not abstract. Line 5 is part of the crude supply chain serving the upper Midwest and eastern Canada. Refineries are not interchangeable; they are configured for particular crude slates and particular delivery routes, and a plant that loses its pipeline feed does not simply switch to another one at the same cost. Replacement barrels would have to arrive by rail, marine or an alternative pipeline route, each of which carries higher unit costs and, in the case of rail, its own safety record.

That is why a shutdown scenario is treated as a cross-border diplomatic issue rather than a purely local permitting dispute. Product markets in Ontario and Quebec, and refining and propane supply in Michigan and neighbouring states, sit downstream of the same decision. A disruption would not stay contained to the company's income statement.

What Is Actually at Stake for Enbridge

For shareholders, Line 5 is a binary embedded inside an otherwise diversified pipeline and utility business. Enbridge operates a very large network; no single line defines the company. But the range of outcomes here is unusually wide for a regulated-style infrastructure owner, and that is what keeps the story on the risk register.

The plausible outcomes fall into three groups:

• Tunnel proceeds. Enbridge spends capital, removes the open-water exposure that underpins most of the legal challenge, and secures the route for the long term. The cost is capital and years of construction.
• Extended litigation. The line keeps operating under legal cloud while permits and appeals grind on. This is the status quo, and it carries a persistent discount in how the market prices the asset.
• Forced shutdown or rerouting. The most damaging case, involving lost throughput, stranded capital and a cross-border dispute over an operating asset.

Markets rarely price a low-probability, high-impact legal event cleanly. They tend to price it as a lingering uncertainty discount, which is one reason single-day moves in the shares are a poor guide to how the case is going.

The Signals Worth Tracking

Three things will tell investors more than any press statement. First, whether state-level permits for the tunnel advance or stall — permitting milestones are the only concrete evidence that the federal position is translating into progress on the ground. Second, whether the dispute escalates into a formal treaty-level matter between Ottawa and Washington, which would change the venue and the leverage. Third, whether Enbridge commits incremental capital to the tunnel, since capital allocation is the clearest signal a company can send about what it expects the outcome to be.

There is a wider point buried in this case. Cross-border energy infrastructure in North America was largely built in an era when the relevant approvals were federal and the politics were quieter. The current legal architecture gives states real veto power over assets whose economics are continental. Line 5 is the highest-profile test of that tension, and whatever precedent emerges will be read carefully by every operator with a pipe crossing a state line or an international one.

For now, the line runs, the tunnel is unbuilt, and the case sits where it has sat for years: in court, with Washington on one side and two state capitals on the other.

Frequently asked questions

What is Line 5?

Line 5 is an Enbridge crude oil and natural gas liquids pipeline that crosses the border between Canada and the United States and passes beneath the Straits of Mackinac in Michigan. It forms part of the crude supply chain serving refineries in the upper Midwest and eastern Canada, which is why any interruption is treated as a cross-border energy security question.

What is the Line 5 tunnel project?

Enbridge has proposed encasing the Straits of Mackinac crossing inside a bored tunnel rather than leaving pipe exposed on the lakebed. The intent is to eliminate the open-water rupture scenario that drives most of the opposition. Critics argue the tunnel extends the operating life of a line they want shut down permanently instead of replaced.

What did the EPA decide?

The Environmental Protection Agency under the Trump administration has come out in support of Enbridge's Line 5 tunnel proposal. That federal backing changes the political balance around the project, but it does not by itself override state-level permitting authority, which remains with Michigan and Wisconsin regulators and courts.

How did Enbridge shares trade on the news?

Enbridge (ENB) was quoted at 46.48 at 18:45 GMT on Sept. 29, 2026, down 1.04% from a previous close of 46.97, within a session range of 46.38 to 46.91. That underperformed the S&P 500 tracker, which was down 0.09% at $764.91 on the same day.

Why are Michigan and Wisconsin opposing the pipeline?

Both states have pressed Enbridge over Line 5 on environmental grounds, with the potential consequences of a spill in the Great Lakes region at the centre of the case. Because permitting and land-use authority sit partly at state level, both states retain meaningful legal and regulatory leverage over an asset whose economics are continental.

What would a shutdown mean for fuel supply?

Refineries are configured for specific crude slates and delivery routes, so a plant losing pipeline supply cannot cheaply switch sources. Replacement barrels would move by rail, marine or alternative pipeline at higher cost. That is why the dispute is framed as a North American energy security issue rather than a purely local permitting matter.

Sources

• Line 5 Pipeline Remains Buffeted On All Sides — Forbes Business

Photo: belief33 · Pixabay Content License — source