Coeur Alaska, Inc. (Coeur) (defendant) was a mining company that sought to open a gold mine north of Juneau, Alaska. Coeur obtained a permit from the U.S. Army Corps of Engineers (Corps) (defendant) for the discharge of crushed rock and water, referred to as slurry, into the Lower Slate Lake. Ultimately, the discharges would raise the lake bed 50 feet and increase the total size of the lake from 23 to 60 acres. The Southeast Alaska Conservation Council (SEACC) (plaintiff), an environmental interest group, filed suit in federal court against the Corps alleging it lacked the authority to issue the permit. Rather, SEACC claimed the Environmental Protection Agency (EPA) had sole jurisdiction to issue the permit under § 402 of the Clean Water Act. Coeur and the State of Alaska intervened as defendants. The district court concluded there was no actionable claim and granted defendants’ motion for summary judgment. SEACC appealed. The court of appeals reversed and concluded that EPA had exclusive authority to issue the permit in question. The U.S. Supreme Court granted certiorari to review.