City of Guyton v. Barrow. Dunn v. Barrow.

Summary

The court held that Georgia's antidegradation rule does not require the Environmental Protection Division to conduct an antidegradation analysis before issuing a permit for a nonpoint-source land application system. Although the regulation mentions both point and nonpoint sources, its text, structure, and federal legal context show that the analysis requirement applies only to point sources. Because the regulation was unambiguous after applying ordinary interpretive tools, the court did not decide whether judicial deference is owed to an agency's interpretation of an ambiguous regulation.