Can one nation, consistent with international trade law, tax imports or otherwise treat them differently based on the CO2 emitted in another country during production of the import? This Article analyzes the General Agreement on Tariffs and Trade (GATT), relevant World Trade Organization (WTO) decisions; and the considerable amount of scholarship regarding Border Thx Adjustments (BTAs) and concludes that such treatment ofimports is legally permissible. In 2013, the European Union (EU) will vote on a proposed rule that seeks to classify crude oil coming into E. U refineries based on "life-cycle greenhouse gas emissions," including CO2 emitted during extraction. Canada, seeking to protect the crude being jumped from Alberta's massive bitumen deposits (the same crude that would feed the controversial Keystone XL pipeline), has threatened to challenge the legality of the proposed E.U. rule before the WTO. The proposed E.U. rule would have siqnfficant implications, as technological advancements have allowed for a new boom in oil extraction from unconventional sources such as bitumen in Alberta and shale in North Dakota. These new extraction techniques emit more carbon dioxide than conventional oil drilling As such, the proposed E.U. rule would affect many nations' exports. Perhaps more siqnfflcantly, the proposed E.U. rule would be the first to base its treatment of an imported product on greenhouse gas emissions that occur in another country. In that sense, it implicates the oft-floated idea of broader BTAs pursuant to which a carbon-conscious nation would tax all imports based on the carbon conswned or greenhouse gases emitted during production. A production-based carbon BTA would provide a tool for carbon-pricing nations, which are frustrated by post-Kyoto climate negotiations, to begin taxing imports from nations such as the U.S. and China, both of which have not adopted carbon -pricing policies. This Article concludes that both the proposed E.U. rule and a broader production-based carbon BTA are legally permissible. Prior analyses reaching a contrary conclusion (or, more commonly, reaching no conclusion at all as to the legality of a production-based carbon BTA) have created obstacles to the legality of such a system where none exist. [ABSTRACT FROM AUTHOR]