Abstract
Based on analysis of a large number of recent domestic court cases on matters of customary international law (2000–2014), this article demonstrates that, rather similar to the International Court of Justice, domestic courts do not normally identify customary norms of customary international law on the basis of the textbook method of ascertaining a general practice accepted as law. Rather, they tend to outsource the determination of custom to treaties, non-binding documents, doctrine or international judicial practice. Sometimes, it appears that domestic courts simply assert, without citing persuasive practice authority, the existence of a customary norm. In rare cases, however, domestic courts do engage in extensive analysis.
Highlights
In the formalist understanding of the sources of international law,1 a norm becomes a norm of international law insofar as it has been generated by accepted processes of international law formation
They tend to outsource the determination of custom to treaties, non-binding documents, doctrine or international judicial practice
It appears that domestic courts assert, without citing persuasive practice authority, the existence of a customary norm
Summary
In the formalist understanding of the sources of international law, a norm becomes a norm of international law insofar as it has been generated by accepted processes of international law formation. The focus of the examination has been placed on the methods or techniques used by domestic courts to identify norms of customary international law, with a view to identifying methodological categories. In this regard, four particular methods for the assessment by the Court of evidence of customary law have played an important role: (1) referring to multilateral treaties and their travaux preparatoires, (2) referring to UN resolutions and other non-binding documents which are drafted in normative language, (3) considering whether an established rule applies to current circumstances as a matter of deduction and (4) resorting to an analogy’). See Yee (2016), p. 37 (‘The AALCOIEG agreed that the two-element approach was the proper one but was very concerned about the uneven rigor with which international courts and tribunals applied it in the identification of customary international law rules in their decisions, in identification operations which were sometimes described as ‘‘pragmatic’’, ‘‘truncated’’, ‘‘incomplete’’, ‘‘untidy’’ or ‘‘assertive’’’). 24 See on this e.g., Roberts (2011), p. 62; Ryngaert (2017)
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