Public trust doctrine

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The public trust doctrine is the principle that the sovereign holds in trust for public use some resources such as shoreline between the high and low tide lines, regardless of private property ownership.[1][2]


The ancient laws of the Roman Emperor Justinian held that the sea, the shores of the sea, the air and running water was common to everyone. The seashore, later defined as waters affected by the ebb and flow of the tides could not be appropriated for private use and was open to all. This principle became the law in England as well. In the Magna Carta in England centuries later public rights were further strengthened at the insistence of the nobles that fishing weirs which obstructed free navigation be removed from rivers.

These rights were further strengthened by later laws in England and subsequently became part of the common law of the United States as established in Illinois Central Railroad v. Illinois, 146 U.S. 387 (1892). In that case the Illinois Legislature had granted an enormous portion of the Chicago harbor to the Illinois Central Railroad. A subsequent legislature sought to revoke the grant, claiming that original grant should not have been permitted in the first place. The court held that common law public trust doctrine prevented the government from alienating the public right to the lands under navigable waters (except in the case of very small portions of land which would have no effect on free access or navigation).

The public trust applies to both waters influenced by the tides and waters that are navigable in fact. The public trust also applies to the natural resources (mineral or animal) contained in the soil and water over those public trust lands.


This doctrine has been primarily significant in two areas: land access and use, and natural resource law. In 2013, Cambridge University Press released a book written by Mary Christina Wood called "Nature's Trust, Environmental Law for a New Ecological Age" that advocated for applying the public trust doctrine to the atmosphere in what is commonly referred to as atmospheric trust litigation.[3]

Navigable waters[edit]

The doctrine is most often invoked in connection with access to the seashore. In the United States, the law differs among the fifty states but in general limits the rights of ocean front property owners to exclude the public below the mean high tide line.

Massachusetts and Maine (which share a common legal heritage) allow private ownership as far as the mean low tide line but allow public access betwen the low and high tide lines for "fishing, fowling and navigation," traditional rights of public access going back to the Colonial Ordinance of 1647. Maine's Supreme Court in 2011 expanded the public trust doctrine by concluding fishing fowling and navigation are not an exclusive list; the court allowed the general public to cross private shoreline for scuba diving.[2]

Some states allow free access to the intertidal zone for walking, swimming, sunbathing, etc. This does not always include the right to cross private land to reach the shore but prevents private owners from excluding the public below the mean high tide line. This line is calculated as the average high tide line of a 14.1 year cycle which means in practical terms that neither property owners nor the public are likely to be able to identify its precise location. On tidal waters the burden of proof therefore falls to the property owner as it would be trespassing for the public to willfully cross above the mean high tide line but not to miscalculate its location. On smaller creeks and streams the burden of proof falls on the party claiming the navigable servitude, Harrison v. Fite, 148 F. 781 (1906) .

Natural resources[edit]

The doctrine has also been used to provide public access across and provide for continued public interest in those areas where land beneath tidally influenced waters has been filled. In some cases, the uses of that land have been limited (to transportation, for instance) and in others, there has been provision for public access across them.

The doctrine has been employed to assert public interest in oil resources discovered on tidally influenced lands (Mississippi, California) and has also been used to prevent the private ownership of fish stocks and crustacean beds.

In most states in the United States, lakes and navigable-in-fact streams are maintained for drinking and recreation purposes under a public-trust doctrine.

The public trust doctrine at Mono Lake, California[edit]

Mono Lake, an ancient saline lake in California's Eastern Sierra, was long threatened by the diversion of its tributary streams south to Los Angeles, thereby lowering the water levels. In 1983 the California Supreme Court ruled in National Audubon Society v. Superior Court that Mono Lake is a public trust resource of the state of California. This was an important victory for the Mono Lake Committee, the National Audubon Society, and other advocates for[according to whom?] the lake. Expanding the ancient doctrine to include recreational and aesthetic values and the importance of the lake to wildlife, the Court decreed that Mono Lake has "public trust values" that the state has an obligation to maintain. In the words of the Court, "The public an affirmation of the duty of the state to protect the people's common heritage of streams, lakes, marshlands and tidelands."

The Court ruled that the water rights of Los Angeles and the public trust values of Mono Lake had to be more fairly balanced, and that the water rights of the City of Los Angeles would have to be revisited to assure proper public trust protections. The Mono Lake Committee has been working since 1978 to achieve this balance.[4]

See also[edit]

Further reading[edit]


  1. ^ National Working Waterfront Network (July 22, 2015). "Public Trust Doctrine". Retrieved July 22, 2015. 
  2. ^ a b Evan Parrott (October 1, 2011). "Maine's Public Trust Doctrine Continues to Evolve" (PDF). Retrieved July 22, 2015. [The] Maine Supreme Judicial Court affirmed . . . that the public has a right to walk across [privately owned] inter-tidal lands to reach the ocean for purposes of scuba diving. 
  3. ^ Wood, Mary Christina (19 September 2014). "A New Approach to Environmental Law". Moyers and Company. Retrieved 4 June 2015. 
  4. ^
  5. ^ David Bollier, "Mary Wood’s Crusade to Reinvigorate the Public Trust Doctrine", Resilience, Feb. 12, 2014.

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