Conceptual Confusion and Methodological Deficiencies: Some Ways that Theories on Customary International Law Fail

Andrew Guzman declares that customary international law is in trouble. I disagree. It is those who seek to explain it who are in trouble. Theoretical efforts are plagued with descriptive insufficiencies (for example, the formation of various customary norms takes place within a heterogeneous, opaque process that resists any general and meaningful description in specific cases), systemic uncertainties (for example, locating the source of rules that govern the formation of customary norms), semantic problems (such as what exactly is general practice) and the divergence of conceptions articulated within international practice. These difficulties, which hamper a better understanding of international law itself, originate from the conceptual level. This article will therefore focus on certain symptomatic conceptual and methodological problems. Nine of them are outlined, and three will be analysed in greater detail, namely the relationship between opinio juris and acceptance, the characteristics of the concept "general practice" and the failure of attempts to describe customary international law by dichotomies. As a conclusion, the author identifies seven requirements of, and assumptions about, a possible, workable theory of customary international law.