In the 1988 case Marsh v. Oregon Natural Resources Council, the U.S. Supreme Court ruled in favor of Secretary of Army John O. Marsh Jr., stating that a complete Environmental Impact Statement (EIS) does not need to be prepared every time new information comes to light after an initial EIS has been completed and approved under the National Environmental Policy Act (NEPA). The dispute arose when Oregon Natural Resources Council challenged the construction of Elk Creek Dam arguing that significant new data about potential environmental impacts had emerged since completion of original EIS, necessitating a revised or supplemental statement. However, Justice Harry Blackmun writing for majority held that agencies are only required to prepare supplements if there remains major federal action yet to occur and if changes would result in significant environmental impact not previously evaluated.

In the dissenting opinion for Marsh v. Oregon Natural Resources Council, it was argued that the Army Corps of Engineers should have been required to prepare a supplemental Environmental Impact Statement (EIS) after changing their plans for a dam on the Middle Snake River. The dissenters believed that this change significantly altered environmental impacts and thus warranted further review under National Environmental Policy Act (NEPA). They contended that NEPA requires agencies to reassess their actions when significant new circumstances or information arise, which they believe happened in this case with changes in salmon spawning patterns and other ecological factors. Furthermore, they disagreed with majority's interpretation of "reasonably foreseeable" impacts as being too narrow and not fully considering potential long-term effects on fish populations. Thus, they felt the decision undermined NEPA’s goal of ensuring informed decision-making about projects affecting environment.