This Article addresses a longstanding puzzle about customary international law (CIL): How can it be, at once, so central to the practice of international law—routinely invoked and applied in a broad range of settings—and the source of such persistent confusion and derision? The centrality of CIL suggests that, for the many people who use it, it is not only comprehensible but worthwhile. They presumably use it for a reason. But then, what accounts for all the muddle and disdain? The Article argues that the problem lies less in the everyday operation of CIL than in the conceptual baggage that is brought to bear on it. Most contemporary accounts of CIL reflect what can be called a “rulebook conception.” They presuppose that, in order for a given proposition to be CIL, it must apply more or less in the same way in all cases of a given type, rather than fluctuate without established criteria from one situation to the next. This rulebook conception is wrong. It does not accurately describe the range of normative material that global actors, in the ordinary course, use and treat as CIL. And because it is wrong, it systematically sows confusion and leads analysists to devalue CIL as a kind of international law. We should stop imagining that CIL operates like a rulebook and should recognize that it is an inherently contingent and variable kind of law.

中文翻译：

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理解习惯国际法

这篇文章解决了关于习惯国际法 (CIL) 的一个长期难题：它怎么会同时成为国际法实践的核心——在广泛的环境中经常被援引和应用——以及这种持续混淆和应用的根源？嘲笑？CIL 的中心性表明，对于使用它的许多人来说，它不仅易于理解，而且值得。他们大概是出于某种原因使用它的。但是，是什么解释了所有的混乱和不屑？文章认为，问题不在于习惯国际法的日常运作，而在于对其施加的概念包袱。大多数当代对习惯国际法的描述反映了所谓的“规则手册概念”。他们预先假设，为了使一个给定的命题成为 CIL，它必须或多或少地以相同的方式应用于给定类型的所有情况，而不是在没有既定标准的情况下从一种情况波动到另一种情况。这个规则手册的概念是错误的。它没有准确描述全球行为者在日常过程中使用和视为习惯国际法的规范材料的范围。并且因为它是错误的，它系统地散播混乱并导致分析人员贬低作为一种国际法的习惯国际法。我们应该停止想象习惯国际法像规则手册一样运作，而应该认识到它是一种内在的偶然和可变的法律。它系统地散播混乱并导致分析家贬低习惯国际法作为一种国际法的价值。我们应该停止想象习惯国际法像规则手册一样运作，而应该认识到它是一种内在的偶然和可变的法律。它系统地散播混乱并导致分析家贬低习惯国际法作为一种国际法的价值。我们应该停止想象习惯国际法像规则手册一样运作，而应该认识到它是一种内在的偶然和可变的法律。