One of the main underpinnings of environmental law in the United States is the Public Trust Doctrine (“PTD”). The doctrine, which is found primarily in state common law, requires states to manage certain natural resources for the benefit of the public. While the PTD has traditionally been used to manage water resources, recent lawsuits have sought to expand the doctrine to include natural resources that have been impacted by climate change.

What Is the PTD?

The United States’ PTD is commonly viewed as having roots in Roman civil law. In the sixth century, Roman law texts that “by the law of nature these things are common to all mankind: the air, running water, the sea, and consequently the shores of the sea.” This has been interpreted to mean that air, water, and beaches were common property which would be owned by no one and instead belonged to people as a whole. That idea was reaffirmed in the Magna Carta and eventually incorporated into English common law. However, when this concept was assumed into English common law it was altered slightly by assigning ownership of common property to the king to keep as a trustee for the benefit of the people. When the United States was developing its legal system, it adopted the English common law, in some cases refining certain aspects of the law as the country developed. When courts began to consider the PTD, they reasoned that ownership of water and underlying lands had transferred to citizens of states when the state gained statehood, ultimately interpreting the PTD much closer to the original Roman concept.

The first Supreme Court case to address the PTD, Martin v. Waddell, 41 U.S. 367 (1842), affirmed the doctrine and held that the public maintained a common right to fish in navigable and tidal water because those waters and their underlying lands were kept in trust by the state for the common use of the people. In this case, the Supreme Court established the basic concept of the PTD in the United – that resources subject to the PTD are entrusted to the care of government to be managed in trust for the benefit of the public. Traditionally, the PTD was applied to navigable waters, submerged lands beneath navigable waters, and tidelands. Those resources were managed to protect the public’s right to engage in commerce, navigation, and fishing.

The Supreme Court revisited the PTD again in both Illinois Central R. Co. v. Illinois, 146 U.S. 387 (1892), and Greer v. Connecticut, 161 U.S. 519 (1896). In Illinois Central R. Co., the Court considered the responsibility of the states as trustees under the PTD. First, the Court reaffirmed that states held navigable waters and the lands beneath them in trust for the benefit of the public, but went on to note that states may allow private entities to use trust resources, and to obtain property rights in those resources. However, even though states may allow private entities to use and acquire rights to trust resources, the PTD still required that as trustees the states must ensure that the underlying purposes of the public trust are fulfilled.

In Greer, the Supreme Court expanded the PTD to include wildlife. Specifically, the Court concluded that states held all the wildlife within their borders in public trust, and could therefore regulate the management and harvest of wildlife. Although the application of Greer has evolved, the general idea that wildlife can be managed according to the PTD remains. Prior to this case, the PTD had primarily been viewed as applying to waterways and the lands beneath them. Greer showed that the doctrine had the potential to be more expansive.

Power of States and Federal Government Under the PTD

In general, states are considered the primary trustees of public trust resources. Because of this, the PTD is shaped by state institutions and can vary from jurisdiction to jurisdiction. A few states have incorporated the PTD into their constitutions. For example, the Constitution of the State of Hawai’i requires that “All public natural resources are held in trust by the State for the benefit of the people.” HAW. CONST. art. XI, § 1. However, it is more common for states to use legislation to administer the PTD.

Regardless of how a state implements the PTD, courts will play an important role in ensuring that trust resources are being managed for the public’s benefit. In Priewe v. Wisconsin State Land & Improvement Co., 93 Wis. 534 (1896), the Wisconsin Supreme Court held that it was the role of courts to make the final determination of whether a certain act is done for a public or a private purpose. Although that case is only applicable in Wisconsin, it is generally true that courts have a responsibility to determine whether a state legislature has acted according to its obligation as trustee to maintain the public trust.

Generally, the PTD has been viewed solely as a function of state law. As recently as 2012, the Supreme Court stated that “the public trust doctrine remains a matter of state law” in PPL Montana, LLC v. Montana, 565 U.S. 576 (2012). The federal government has often taken the position that there is no federal PTD, and that instead the doctrine is rooted entirely in state law. However, that view is not universal. Some argue that evidence for a federal PTD can be found in the Property Clause, the Commerce Clause, and the Supremacy Clause of the United States Constitution. Together, these provisions give Congress the power to regulate the “territory or property” of the United States, commerce among the several states, and the ability to set “the supreme law of the land.” Several federal laws regulating wildlife, such as the Endangered Species Act and the Migratory Bird Treaty Act, have been grounded in one or more of these clauses.

Because PTD cases have tended to involve natural resources controlled by states, there has been very little case law discussing the federal PTD. However, some federal courts have seemed to recognize that the federal government may play a trustee role under the PTD. In U.S. v. 1.58 Acres of Land, 523 F.Supp. 120, 124 (D. Mass. 1981), a federal court in Massachusetts held that “the trust impressed upon this property is governmental and administered jointly by the state and federal governments by virtue of their sovereignty.”

Ultimately, the most common theory is still that the PTD is primarily an issue of state law, not federal.

Recent Use of the PTD

In recent years, several cases have been filed in both state and federal courts arguing that the PTD requires state governments to take more aggressive action in battling climate change. Perhaps the most well-known of these recent PTD cases is Juliana v. U.S., No. 18-36082 (9th Cir. 2020), which was originally brought in 2015 by 21 youth plaintiffs against the United States. In that case, the plaintiffs argued that the federal government had violated its PTD duties by both encouraging and allowing the use of fossil fuels. In response, the government has argued that there is not federal PTD, and that even if there was, it would not extend to the climate or atmosphere. While the lower court initially concluded that the plaintiffs had appropriately stated a public trust claim and could bring that argument before the court, the Ninth Circuit Court of Appeals ruled that the plaintiffs did not have the appropriate standing to bring their case. However, the Ninth Circuit’s conclusion that plaintiffs standing was not based on the PTD, but was instead based on the court’s finding that the issue raised by the plaintiffs was better suited for the political branches of government to handle. Therefore, the issue of whether a federal PTD exists and could be applied to climate change remains undecided.

In state court, plaintiffs have also brought claims arguing that the PTD should be expanded to address climate change. Most recently, in Chernaik v. Brown, 367 Or. 143 (Or. 2020), the Oregon Supreme Court rejected claims brought by plaintiffs who argued that under the PTD, the state of Oregon had an affirmative obligation to reduce greenhouse gas emissions. The lawsuit was originally filed in 2011, with the plaintiffs arguing that Oregon had failed to uphold its PTD duties by failing to adequately regulate and reduce carbon dioxide emissions. Specifically, the plaintiffs sought declaratory relief from the court that the Oregon PTD covered natural resources such as atmosphere, wildlife, and fish. Ultimately, the Oregon Supreme Court ruled that the plaintiffs had failed to establish a legal basis for expanding the PTD in Oregon beyond its current limits. Additionally, the court concluded that the legal theories raised by the plaintiffs could not result in a finding that the PTD required Oregon to protect public trust resources from the effects of climate change.

While the courts in both Juliana and Chernaik declined to expand the PTD or conclude that it required governments to prevent trust resources from experiencing the effects of climate change, that does not preclude future courts from reaching different conclusions. It is likely that plaintiffs will continue to raise PTD claims in climate change lawsuits, and it is unclear how different jurisdictions will rule.


The PTD continues to be a foundational aspect of United States environmental law. Although on its surface the doctrine can appear straightforward, questions of what natural resources fall within the public trust, and what the responsibilities of trustees are can complicate the doctrine’s application. Because it is primarily a function of state law, the boundaries of the PTD can vary from jurisdiction to jurisdiction. Agricultural producers, particularly those that maintain a water right, may need to be familiar with how the PTD functions in their state. In some circumstances, the regulation of a waterbody under the PTD for the benefit of the public can affect private water rights. Additionally, producers should be aware that the PTD is a doctrine that can evolve, and may be expanded as courts consider the public trust as it relates to climate change.


To read the court’s opinion in Martin v. Waddell, click here.

To read the court’s opinion in Illinois Central R. Co. v. Illinois, click here.

To read the court’s opinion in Greer v. Connecticut, click here.

To read the court’s opinion in Priewe v. Wisconsin State Land & Improvement Co., click here.

To read the court’s opinion in PPl Montana, LLC v. Montana, click here.

To read the court’s opinion in U.S. v. 1.58 Acres of Land, click here.

To read court opinions and documents from Juliana v. U.S., click here.

To read the court’s opinion in Chernaik v. Brown, click here.