The Public Trust Doctrine is a legal principle derived from English Common Law. Under this doctrine, the waters of the state are a public resource owned by and available to all citizens equally for:
- Purposes of navigation
- Conducting commerce
- Recreation and similar uses
The Public Trust Doctrine trust is not invalidated by private ownership of the underlying land. The doctrine limits public and private use of tidelands and other shoreline areas to protect the public's right to use the waters of the state.
The Public Trust Doctrine does not allow the public to trespass over privately-owned uplands to access the tidelands. It does, however, protect public use of navigable water bodies below the ordinary high water mark
Protecting the public trust is a duty of Washington. The state Shoreline Management Act is one of the primary means by which this duty is carried out. The doctrine requires a careful evaluation of the public interest served by any proposed action. In large part, this requirement is fulfilled by planning and permitting requirements under the Shoreline Management Act.
Local governments should consider public trust doctrine concepts when developing Shoreline Master Programs,
comprehensive plans, and development regulations. There are few "bright lines" because the Public Trust Doctrine is common, not statutory law. This means the extent of its applicability can only be determined by state court decisions. For an introduction to state case law see The Public Trust Doctrine and Coastal Zone Management in Washington State