IILJ Emerging Scholars Paper 20 (2011)

Subsequent Practice and Evolutive Interpretation: Techniques of Treaty Interpretation over Time and Their Diverse Consequences

Julian Arato

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This paper compares two different means of treaty interpretation by which a treaty or treaty provision may change over time: the interpretation and reinterpretation of a treaty on the basis of its evolutive character, and the (re)interpretation of a treaty on the basis of the subsequent practice of the parties. I contend that evolutive interpretation and interpretation based on subsequent practice do not simply refer to two different and distinct phenomena – as a practical matter they constitute two different “techniques of interpretation” which may or may not both be applicable in a particular case, and may sometimes both be applicable but mutually exclusive. The basic problem of the paper revolves around the following question: where the evidence is uncertain, or ambivalent, which technique – if any – should be applied?