NEPA's procedural mandates require agencies to inform their discretion in decisionmaking. An agency that complies with NEPA gives outside influences (the public, lawmakers, other agencies) more information with which to put pressure on that agency, but the original agency retains substantive decisionmaking power regardless. At most, the Corps has abused its discretion—an abuse explicitly immunized by the DFE.

Monday's ruling overturns a March decision by the same Fifth Circuit panel, which held that the USACE was liable for the damages [JURIST report]. The appeal followed a 2009 decision [JURIST report] by the US District Court for the Eastern District of Louisiana [official website] which held that the USACE made "negligent decisions" that "rested on applications of objective scientific principles and were not susceptible to policy consideration," and awarded plaintiffs approximately $720,000. Also in 2009 the Fifth Circuit ruled that several contractors responsible for dredging the Mississippi River, which some claim exacerbated damage from Hurricane Katrina, cannot be held liable [JURIST report] since the contractors were acting under Congress' express authorization.