Henckaerts and Doswald-Beck, 2005.
See, e.g., Akehurst, ‘The hierarchy of the
sourcesofinternationallaw’, 47 Brit. Y.B. Int’l Law
(1974–75) 273; Villiger, Customary International Law and
Treaties , Part III.
Declaration of Paris, Schindler
framework which Walden articulates is compatible with the approach that the International Law Commission adopts in the Conclusions. See O Sender and M Wood , ‘ A Mystery No Longer? Opinio Juris and Other Theoretical Controversies Associated with Customary International Law ’ ( 2017 ) 50 Israel Law Review 299 .
67 Walden (n 59) 99. Emphasis added.
68 See D’Amato (n 56). cf Walden (n 59) 99.
69 M Akehurst , ‘ Custom as a SourceofInternationalLaw ’ ( 1976 ) 1974–75 The British Yearbook of International Law 1 .
70 D’Amato (n 56) 78.
rule of international law to this effect. The further question was, of
course, from where did the customary rule originate? And here Oppenheim invoked a theoretical distinction between sources and causes. As
sourcesofinternationallaw, he allowed only treatise and custom. Yet
these sources had causes, and here elements of natural law crept into
Oppenheim’s jurisprudential system. It was ‘religious and moral reasons’
that had, in this idiom, caused the custom. Likewise, it was a slow moral
development which had caused many of the increasingly codified laws of