Imagine the federal government deciding it wants to restrict how you use your property — your farmland, your coastal lot, your groundwater well. Now imagine it doing so without filing a condemnation proceeding, without offering compensation, and without ever having to justify the action under the Fifth Amendment's Takings Clause. Sound far-fetched? It is happening right now, in courtrooms and regulatory agencies across the country, under the banner of something called the public trust doctrine — and most Americans have never heard of it.
The doctrine itself is not new. Its roots stretch back to Roman law and English common law, and it entered American jurisprudence through a straightforward principle: certain resources — navigable waterways, tidal lands, submerged soils — are held in trust by the government for the benefit of the public and cannot be permanently alienated to private parties. In that original, narrow form, the doctrine is sensible and defensible. The problem is that "narrow" is no longer a word that applies to how it is being used.
From Rivers to the Atmosphere
Over the past two decades, environmental advocates, state attorneys general, and a receptive cohort of judges have been systematically expanding the public trust doctrine far beyond its historical boundaries. The progression has followed a recognizable pattern: accept the doctrine's legitimacy in its traditional domain, then argue that its underlying rationale — that some resources are too important to be left entirely to private control — applies equally to resources that were never part of the original framework.
Beaches were an early target. In states including Hawaii and New Jersey, courts have ruled that the public trust extends to dry sand beach areas above the mean high-tide line — land that, in many cases, is unambiguously private property by deed and longstanding legal title. Hawaii's Supreme Court has been particularly aggressive, interpreting the state constitution's public trust provision to impose affirmative obligations on private landowners and state agencies alike, restricting uses of private land that the owners had every reason to believe were lawfully theirs.
Groundwater has been the next frontier. In states facing water scarcity — particularly in the West — regulators and courts have increasingly invoked public trust principles to restrict private groundwater extraction, even where property owners hold valid water rights under state law. The California Supreme Court's 2014 decision in National Audubon Society v. Superior Court had already established that the public trust could apply to non-navigable tributaries affecting navigable waters. Advocates have used that precedent as a launching pad for far broader claims.
Most audaciously, some legal theorists and at least one state-level proceeding have floated the idea that the atmosphere itself — the air above private and public land alike — is a public trust resource, meaning that carbon emissions from private activity could be regulated under public trust principles rather than conventional statutory authority. The "atmospheric trust litigation" movement, pioneered by University of Oregon law professor Mary Wood, has filed cases in multiple states and federal courts seeking judicial orders compelling emissions reductions on public trust grounds. Most have been dismissed, but the theory has not been abandoned.
The Constitutional Problem Nobody Wants to Name
Here is the core issue that proponents of expanded public trust doctrine consistently decline to address directly: the Fifth Amendment requires that when the government takes private property — or so substantially restricts its use as to constitute a functional taking — it must pay just compensation. This requirement is not optional, and it is not suspended because the government's purpose is environmentally popular.
The Supreme Court established in Lucas v. South Carolina Coastal Council (1992) that a regulation which denies a property owner all economically beneficial use of land constitutes a per se taking requiring compensation. Penn Central Transportation Co. v. New York City (1978) established a broader balancing test for partial regulatory takings. These precedents are binding law.
The public trust doctrine, as currently weaponized, is an attempt to accomplish through common law theory what the Takings Clause would otherwise require the government to pay for. If a state can declare your beachfront lot part of the public trust, restrict your use of it accordingly, and do so without triggering a takings analysis because the restriction derives from the trust doctrine rather than a statute or regulation, the Takings Clause becomes meaningless wherever the doctrine applies. The constitutional protection evaporates not because the underlying property interest has changed, but because the legal theory used to restrict it has been carefully chosen to avoid the compensation requirement.
This is not a coincidence. It is the strategy.
The Strongest Defense — and Its Limits
Serious environmental law scholars argue that the public trust doctrine is not a workaround — it is a pre-existing limitation on the nature of property rights themselves. On this view, property acquired subject to the public trust was never fully private to begin with; the trust encumbrance was always part of the title, even if not explicitly stated. You cannot be "taken" something you never fully owned.
This argument has genuine intellectual force in its traditional domain. If you purchase tidal land knowing that public navigation rights attach to it under longstanding common law, you have fair notice that your ownership is qualified. The compensation argument is weaker in that context.
But the argument collapses when the doctrine is extended to resources — upland private parcels, groundwater, the atmosphere — where no historical public trust encumbrance existed and where property owners had every reasonable expectation of full private ownership. Retroactively declaring that a farmer's groundwater rights, or a developer's dry-sand beachfront, were always subject to a public trust obligation that was simply not previously recognized is not a clarification of pre-existing law. It is a taking dressed in historical costume.
What Is at Stake
The practical stakes extend well beyond environmental policy. If the public trust doctrine can be expanded without limit by judicial decision or regulatory reinterpretation, it becomes a constitutional escape hatch of the first order — a mechanism by which government at any level can restrict private property rights without compensation simply by invoking a sufficiently ancient-sounding legal principle.
Property rights are not a peripheral concern in the American constitutional order. They are foundational to every other right. The ability to own, use, and transfer property free from arbitrary government interference is the material precondition for individual liberty, economic independence, and the kind of civil society that does not depend on government permission for its existence. When that foundation erodes — when the legal theories protecting it are stretched until they cover their opposites — everything built on top of it becomes less secure.
The Supreme Court has occasionally pushed back. Murr v. Wisconsin (2017) and Cedar Point Nursery v. Hassid (2021) both imposed meaningful limits on regulatory maneuvering around the Takings Clause. But the Court has not directly confronted the expanded public trust doctrine in a way that forecloses the most aggressive applications currently being pursued at the state level.
Until it does, green activists will keep using a Roman legal theory to confiscate American property — and the bill will keep going unpaid.
