The theoretical claims for eco-tariffs are rigorously analyzed within a unified framework formed of an international trade model enriched with both a domestic and a global externality. During the course of the analysis the model is modified to analyze an array of contexts for which eco-tariffs have been claimed to improve environmental quality or welfare. The circumstances and conditions are characterised under which such tariffs can be shown to improve environmental quality and social welfare, taking account of general equilibrium effects. The theoretical results are applied in a...