In July 1997, the Council on Environmental Quality (CEQ) published guidance on the applicability of NEPA to proposed federal actions that may have transboundary impacts. The guidance does not expand the range of actions to which NEPA currently applies. An action which does not now fall under NEPA would not be included because of the guidance. The CEQ also noted that many proposed federal actions will not have transboundary effects, and Federal agencies should use the scoping process to identify such actions. For those actions which have the potential to cause transboundary impacts, case law interpreting NEPA has reinforced the need to analyze these impacts regardless of geographic boundaries. The CEQ concludes, “NEPA requires agencies to include analysis of reasonably foreseeable transboundary effects of proposed actions in their analysis of proposed actions in the United States. Such effects are best identified during the scoping stage, and should be analyzed to the best of the agency's ability using reasonably available information. Such analysis should be included in the EA or EIS prepared for the proposed action.”
The U.S., Canada, and Mexico are negotiating a Transboundary Environmental Impact Assessments (TEIA) agreement that will require each country to assess any significant transboundary environmental impacts of proposed projects.
Executive Order 12114 (Environmental Effects Abroad) requires Federal agencies to analyze in NEPA documents the significant impacts of proposed projects on the environment outside the U.S.