This article offers the justification for a type of carbon customs union in which countries with a diverse range of high-ambition domestic climate measures would adopt a common external tariff on carbon intensive imports from countries outside the union. We explain why any pragmatic approach to carbon border measures (CBMs) is likely to create problems under prevailing interpretations of the World Trade Organization's (WTO) primary rules. Given the urgency of the climate crisis and the fact that the legality of a CBM – no matter how designed – will be a question of first impression for any WTO dispute panel, WTO consistency should take a backseat to considerations of domestic legal and political feasibility in designing a CBM. Instead of trying to fit a CBM into current understandings of WTO rules, WTO members should renegotiate WTO rules to permit a range of aggressive, but likely trade-restrictive, decarbonization measures. Having said that, we also recognize that WTO negotiations may take longer than optimal from a decarbonization standpoint. We therefore suggest an approach that would allow WTO members to take advantage of flexibilities that existing WTO rules afford.

中文翻译：

---

碳边界措施的务实方法

本文提供了一种碳关税同盟的理由，在这种同盟中，拥有各种雄心勃勃的国内气候措施的国家将对来自联盟以外国家的碳密集型进口采取共同的外部关税。我们解释了为什么任何务实的碳边界措施 (CBM) 方法都可能在对世界贸易组织 (WTO) 主要规则的普遍解释下产生问题。鉴于气候危机的紧迫性以及 CBM 的合法性（无论设计如何）将是任何 WTO 争端小组的第一印象问题，WTO 的一致性应该让位于对国内法律和政治可行性的考虑。设计 CBM。与其试图将 CBM 纳入当前对 WTO 规则的理解，世贸组织成员应重新谈判世贸组织规则，以允许采取一系列激进但可能限制贸易的脱碳措施。话虽如此，我们也认识到，从脱碳的角度来看，WTO 谈判可能需要比最佳时间更长的时间。因此，我们建议采用一种方法，允许 WTO 成员利用现有 WTO 规则提供的灵活性。