The National Environmental Policy Act (NEPA) is a United States environmental law that promotes the enhancement of the environment and established the President's Council on Environmental Quality (CEQ). The law was enacted on January 1, 1970. To date, more than 100 nations around the world have enacted national environmental policies modeled after NEPA.
NEPA's most significant outcome was the requirement that all executive federal agencies prepare environmental assessments (EAs) and environmental impact statements (EISs). These reports state the potential environmental effects of proposed federal agency actions. NEPA does not apply to the President, Congress, or the federal courts.
This summary is from Wikipedia.