Editors' Summary: Environmental regulations can be complex and confusing. Even sophisticated companies sometimes have trouble deciphering the regulations. A number of defendants have argued that environmental penalties should be reduced or eliminated when regulations are ambiguous or confusing. In the recent case of Rollins Environmental Services (NJ), Inc. v. EPA, the D.C. Circuit addressed this "regulatory confusion" defense. The court set aside a $ 25,000 penalty for violation of EPA's PCB regulations based on the ambiguity of the regulations. This Article analyzes the Rollins decision and explores how other courts have responded to regulatory confusion claims. The Article also discusses the related issue of how much deference courts give agency interpretations in enforcement actions. The author concludes that Rollins leaves many questions open, but should provide defendants with some foundation for avoiding or mitigating civil penalties where a defendant tries to follow an ambiguous regulation and the government is pursuing an expanded construction of the regulation.