The North American Model of Wildlife Conservation is a set of principles that has guided wildlife management and conservation decisions in the United States and Canada. Although not formally articulated until 2001, the model has its origins in 19th century conservation movements, the near extinction of several species of wildlife (including the American Bison) and the rise of sportsmen with the middle class. Beginning in the 1860s sportsmen began to organize and advocate for the preservation of wilderness areas and wildlife. The North American Model of Wildlife Conservation rests on two basic principles – fish and wildlife are for the non-commercial use of citizens, and should be managed such that they are available at optimum population levels forever. The North American Model of Wildlife Conservation is a set of principles that has guided wildlife management and conservation decisions in the United States and Canada. Although not formally articulated until 2001, the model has its origins in 19th century conservation movements, the near extinction of several species of wildlife (including the American Bison) and the rise of sportsmen with the middle class. Beginning in the 1860s sportsmen began to organize and advocate for the preservation of wilderness areas and wildlife. The North American Model of Wildlife Conservation rests on two basic principles – fish and wildlife are for the non-commercial use of citizens, and should be managed such that they are available at optimum population levels forever. The North American model has no direct legal powers, but rather has become the basis for policies developed by the Boone and Crockett Club, the Association of Fish and Wildlife Agencies, The Wildlife Society, and other conservation groups. The model has been widely accepted by wildlife professionals, incorporated into U.S. state agencies, and endorsed by professional organizations and teaching institutions. The core principles of the Model are elaborated upon in the seven major tenets: In the North American Model, wildlife is held in the public trust. This means that fish and wildlife are held by the public through state and federal governments. In other words, though an individual may own the land up which wildlife resides, that individual does not own said wildlife. Instead, the wildlife is owned by all citizens. With origins in Roman times and English Common law, the public trust doctrine has at its heart the 1842 Supreme Court ruling Martin V. Waddell. Commercial hunting and the sale of wildlife is prohibited to ensure the sustainability of wildlife population. This principle holds that unregulated economic markets for game and nongame wildlife are unacceptable because they privatize a common resource and lead to declines. The Lacey Act of 1900 effectively made market hunting illegal in the United States, and the Migratory Bird Treaty Act of 1918 provided international protections from the market. Wildlife is allocated to the public by law, as opposed to market principles, land ownership, or other status. Democratic processes and public input into law-making help ensure access is equitable. Laws regulating access to wildlife include the 1940 Bald and Golden Eagle Protection Act, Endangered Species Preservation Act and Fur Seal Act of 1966, the Marine Mammal Protection Act of 1972, and the 1973 Endangered Species Act. Under the North American Model, the killing of game must be done only for food, fur, self-defense, and the protection of property (including livestock). In other words, it is broadly regarded as unlawful and unethical to kill fish or wildlife (even with a license) without making all reasonable effort to retrieve and make reasonable use of the resource. As wildlife do not exist only within fixed political boundaries, effective management of these resources must be done internationally, through treaties and the cooperation of management agencies. The North American Model recognizes science as a basis for informed management and decision-making processes. This tenet draws from the writings of Aldo Leopold, who in the 1930s called for a wildlife conservation movement facilitated by trained wildlife biologists that made decisions based on facts, professional experience, and commitment to shared underlying principles, rather than strictly interests of hunting, stocking, or culling of predators. Science in wildlife policy includes studies of population dynamics, behavior, habitat, adaptive management, and national surveys of hunting and fishing.