The ancient Roman doctrine guiding modern environmental fights

August 25, 2026

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5 min read

In 1953, Enbridge laid two pipelines across the bottom of the Straits of Mackinac, the narrow waterway separating Michigan’s upper and lower peninsulas. Today, those pipelines—Line 5—carry 23 million gallons of crude oil and natural gas liquids every day from Wisconsin to Ontario, passing directly through one of the world’s largest freshwater ecosystems. The fight over whether that pipeline should stay, be replaced by a tunnel buried beneath the lakebed, or be shut down entirely has generated a tangle of legal battles, including a case that reached the U.S. Supreme Court this year. But the most recent twist—a Michigan Supreme Court ruling that voided a key state permit—turned on an ancient legal principle called the public trust doctrine, a framework that dates back to the Roman Empire and is now being wielded by environmental groups and tribes across the country.

The pipeline and the tunnel

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What you'll learn

1 (00:30) **The Enbridge Line 5 Pipeline Fight** - Introduction to the decades-old controversy over a 1950s-era oil pipeline crossing the Straits of Mackinac in the Great Lakes.
2 (01:15) **Who Is Fighting and Why** - The opposing coalitions and their core arguments.
3 (03:45) **Latest Legal Twists: Federal Permit Approved, State Permit Blocked** - Two simultaneous legal developments in early 2025.
4 (05:12) **Introducing the Public Trust Doctrine** - The ancient legal framework that powered the Michigan Supreme Court decision.
5 (05:55) **The Roman Roots of the Doctrine** - Tracing the idea from Greek Stoic philosophy to the Institutes of Justinian.
6 (07:01) **The Basic Idea: The State as Trustee** - How the doctrine works in practice.
7 (08:29) **How the Doctrine Applies to Line 5** - The specific legal argument in the pipeline case.

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Show Notes

A controversial pipeline project in Michigan has been stuck in legal limbo for years. But this month, the Michigan Supreme Court sided with environmentalists and leaned on an ancient legal framework: the public trust doctrine.

This doctrine, which dates back to the Roman Empire, says that natural resources, like water, belong to the public, and development must do no harm. Legal experts say this argument is cropping up more and more in climate and environmental lawsuits. Joining Flora to get into the details are environment reporter Vivian La, and law professor Oday Salim.

Guests:

Vivian La is the climate solutions reporter for Interlochen Public Radio and Grist in Northern Michigan.

Oday Salim is director of the Environmental Law & Sustainability Clinic and a co-director of the Environmental and Energy Law Program at the University of Michigan Law School.

Transcript will be available after the show airs on sciencefriday.com.

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