The National Environmental Policy Act (NEPA) is a declaration of national policy intent, reflecting a reorientation of priorities to accord with changing environmental values and perceptions. It does not amend the Constitution; it is not a regulation; and it cannot compel the president to administer its principles and provisions in any particular way: Nor can it cause the Congress to activate more fully its potentialities through supplementary legislation and more generous funding.

But although NEPA cannot mandate the policy it declares, it has nevertheless changed public life in four important respects. First, through its declaratory provisions and annual environmental report, it has kept the environmental issue before the American people, the Congress, and the president; second, through the environmental impact statement requirement and associated stipulations regarding program planning, it has altered the decision process in the federal agencies; third, in association with the Freedom of Information Act, it has forced public disclosure of that process and opened the way to public participation in it; and fourth, it has provided a model that has influenced environmental policy legislation among the several states and in a number of nations abroad.²