botswana/namibia - Cour international de Justice

para. 169) went on to refer to the subordinate character of the principle of subsequent practice.
In his words:
"Status of the principle. ..... the principle of subsequent practice may, from one point of view,
be regarded as part of the principle of confirmation already considered (above, 'Miscellaneous
Points', (f)(iii), and in that aspect it must, like the principle of effectiveness, be regarded as
being, in general, subordinate to the principle of the textual and natural meaning - that is to
say, prima facie, it may serve to confirm that meaning if clear, or may afford an extraneous
means of elucidating it, if obscure or ambiguous; but not to change or add to it if no obscurity
or ambiguity exists and the sense is clear according to the natural and ordinary meaning.
Subsequent practice is (on this basis) primarily one of the extraneous means (like recourse to
travaux préparatoires, or consideration of the circumstances existing previous to or when the
treaty was drawn up) of interpreting a text not clear in itself; and, considered as such, it is
chiefly its superior reliability as an indication of the real meaning and effect of a text that
justifies its treatment as an independent major principle of interpretation". (emphasis
supplied). (British Year Book of International Law, Vol. 33 (1957), p.224).
236. This proviso is important in face of the tendency of the Namibian Memorial to confuse
subsequent conduct as a principle of treaty interpretation with prescription and acquiescence.
237. Before leaving the issues of principle, it is necessary to indicate that the Memorial of
Namibia seeks to establish that subsequent practice may be constituted exclusively by the
'silence' or 'inaction' of the parties: see pages 64-5, paragraphs 175-7. And in this context, it is
pointed out that the penultimate draft of Article 31(3)(b) of the Vienna Convention refers to
'any subsequent practice...which establishes the understanding of the parties regarding its
interpretation' (emphasis added) (ibid., page 65, paragraph 177).
238. The Court should be cautious in face of this suggestion that the text of Article 30(3)(b),
which, in its final form, requires practice which 'establishes the agreement of the parties',
should be watered down. The Memorial of Namibia states that the substitution of 'agreement'
in the final version was purely an exercise of the Drafting Committee to ensure uniformity
with the French, Russian and Spanish texts.
239. The reality was that, in the Committee of the Whole of the Vienna Conference, both the
United States and Australia had introduced amendments to insert the word 'common' before
'understanding': see U.N. Conference on the Law of Treaties, Official Records, Documents,
pages 149 and 150. The Australian amendment was before the Drafting Committee when the
final text was adopted of what, at that stage, was Article 27: ibid., pp. 150-1. Against this
background it becomes apparent that the term 'agreement' in the final text was not a drafting
synonym but a point of substance. This is confirmed by the speech of the Australian delegate
in the Committee as a Whole on 19 April 1968. In his words:
'The Australian drafting amendment to sub-paragraph 3(b) had been prompted by the
statement in paragraph (15) of the commentary that the Commission had had the common
understanding of the parties in mind. The idea was clearly expressed in the French and
Spanish texts, and the amendment therefore affected the English text only.' (U.N. Conference
on the Law of Treaties, Official Records, Summary Records, p. 169, para. 60)
240. This episode in the interpretation of the Vienna Convention provides a further illustration
of the Namibian tendency to move away from the text of the Anglo-German Agreement.