NEPA, the National Environmental Policy (not "Protection") Act, articulates general Federal policy favoring protection of the environment, but its major action-forcing mechanism is a requirement that agencies consider the effects of their actions on the "human environment."
Regulations implementing NEPA have been issued by the Council on Environmental Quality (CEQ) in the Executive Office of the President. CEQ is a three-member council of Presidential appointees served by a small staff. The regulations are at 40 CFR 1500-1508 – that is, Title 40 of the Code of Federal Regulations, Parts 1500 through 1508. The regulations apply to all Federal agencies and all agency actions. The basic requirement is to analyze the effects of the action and consider these effects in decisionmaking.
A common "myth" about NEPA is that it applies only to "major federal actions significantly affecting the quality of the human environment" (MFASAQHE). In fact, NEPA applies to ALL agency actions, but types of action with different levels of potential environmental impact receive different levels of consideration. MFASAQHEs must be given the highest level of consideration through preparation of an Environmental Impact Statement (EIS).
For the full text of the NEPA regulations, and links to other pertinent agency regulations and CEQ guidance, see the CEQ NEPANet web page.