High Quality Content by WIKIPEDIA articles! The public trust doctrine is the principle that certain resources are preserved for public use, and that the government is required to maintain it for the public's reasonable use. The ancient laws of the Roman Emperor Justinian held that the seashore that were not appropriated for private use were 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.