Atlantic States Legal Foundation brought a citizen suit under the Clean Water Act against Eastman Kodak, claiming it was discharging pollutants not listed in its state-issued discharge permit. The district court granted summary judgment for Kodak. The appellate court affirmed, holding that under Section 402(k) of the CWA, a permit holder is shielded from citizen suits for discharging unlisted pollutants if it is in compliance with its discharge permit. The EPA's interpretation that not all pollutants need to be limited in a permit is reasonable and entitled to deference. Therefore, Atlantic States could not bring its citizen suit against Kodak.