States today play a major role in implementing and enforcing environmental laws such as the Clean Air Act, Clean Water Act, and the Resource Conservation and Recovery Act. A thirty year review of ESA identified state leadership in species conservation as a necessary element in better conserving the nation's imperiled species, yet the theoretical and practical reasons and applications of an enhanced state role are little understood and have not been subjected to any meaningful analysis.This book, for the first time, presents the legal and policy analysis for federalism considerations in implementing ESA. The book undertakes a comprehensive analysis of the economic rationale for federalism in ESA administration; compares administration of ESA to other major environmental statutes; reviews various tools under the existing Act to enhance state role in species conservation; evaluates major case studies to determine roles the state can play in species conservation and recovery; and concludes with policy recommendations to encourage greater state involvement in species conservation.