In 1972, the National Pollutant Discharge Elimination System (NPDES) was established under the Federal Water Pollution Control Act (the Act) to require those wanting to discharge pollutants into waters to first obtain a permit from the Environmental Protection Agency (EPA). The Natural Resources Defense Council, Inc. (NRDC) (plaintiff) filed suit in federal court against Douglas Costle in his official capacity as Administrator of the Environmental Protection Agency (EPA) (defendant) challenging his decision to exempt certain classes of pollution point sources from the permit requirement. The NRDC argued that Costle lacked authority to exempt any class of point source from the Act’s permit requirements. The district court agreed and granted NRDC’s motion for summary judgment. The EPA appealed.