In the case of Robertson, Chief of the Forest Service, et al. v. Methow Valley Citizens Council et al., 1988, the U.S. Supreme Court ruled that under the National Environmental Policy Act (NEPA), federal agencies are not required to develop a fully detailed plan for mitigating environmental damage before approving a project with significant environmental impact. The dispute arose when Methow Valley Citizens Council challenged approval given by Forest Service and other authorities to construct a ski resort in Okanogan National Forest due to potential harm on local wildlife habitats and air quality concerns from increased traffic congestion. The court held that NEPA merely requires an agency to take a "hard look" at environmental consequences before taking action but does not mandate it must have mitigation plans in place prior to giving approvals or permits for projects with substantial ecological impacts.

In the dissenting opinion for Robertson, Chief of the Forest Service, et al. v. Methow Valley Citizens Council et al., Justice Harry Blackmun argued that the majority's decision undermined key provisions of The National Environmental Policy Act (NEPA). He believed that NEPA required federal agencies to not only identify potential environmental impacts but also to develop and consider mitigation measures before making any irreversible commitments. In his view, by allowing a project with significant environmental consequences to proceed without requiring specific plans for mitigating these effects beforehand, the court was effectively reducing NEPA’s mandate into a mere paperwork exercise. This interpretation could potentially allow harmful projects to move forward based on vague promises of future mitigation which may or may not be effective or even implemented at all.