Treaty Interpretation And The Incorporation Of Extraneous Legal Rules

Abstract This paper considers under what circumstances, and for what reasons, an international tribunal may want to range beyond the primary text of a treaty to determine its ‘correct’ meaning; such extraneous legal material potentially including rules of customary international law, other treaties between the parties, general principles of law, and documents of a ‘soft law’ nature. The paper suggests a variety of ‘mechanisms’ by which a tribunal may undertake a broader interpretative approach, though all ultimately raise the same inevitable tension between accusations of judicial activism and counter-arguments of inflexibility and insularity. Nevertheless, many tribunals and individual judges continue to utilize such techniques, particularly noticeable in some recent environmental disputes. The paper will conclude with a note of caution; that though such interpretations are becoming an increasingly significant part of modern judicial decision-making—something that is generally to be welcomed—tribunals must concurrently take care to ensure that they remain within the accepted parameters of the adjudicative function.