Embedded within the structure of much American environmental regulation is a distinction between the new and the existing. Existing products or sources of pollution are often grandfathered out of new regulatory requirements or receive other forms of transition relief. Such treatment reflects a recurrent political challenge facing makers of environmental policy: whether and how to mitigate regulatory burdens when policy change upsets settled expectations and investment commitments.

This dissertation first presents a survey of transition policies in various areas of environmental regulation, and then explores whether and how these policies might be explained by existing theories of regulation. The next four chapters present detailed case studies drawn from the trucking and pesticide industries, describing both the emergence of transition relief and the later efforts of policymakers to address problems arising out of this relief. These case studies demonstrate that although numerous variables affect transition policy, the degree of transition relief in a regulatory program is substantially influenced by the cost impacts of that program on incumbents, a factor which in turn is shaped by the composition and competitive dynamics of the regulated industry.