The inductive and deductive methods in customary international law analysis: traditional and modern approaches.

Author:Worster, William Thomas
Position::IV. The Interplay of Deduction and Induction in Customary International Law D. Establishing the Types and Forms of Evidence through V. Conclusion, with footnotes, p. 483-521
  1. Establishing the Types and Forms of Evidence

    Once the tribunal has determined that it may test the hypothesis of the law by a sampling method, the court determines that certain acts or facts can constitute evidence of state practice and opinio juris. (149) This is also a deductive step. There is no clear agreement on which volitional manifestations constitute "acts," and which of those acts qualify as "state practice." (150) There also does not appear to be any distinction between types of questions and the types of evidence more suitable for each question. (151)

    1. Qualifying Categories of Actors

      The first aspect of this inquiry is the nature of the actor, and whether it qualifies as a state. State practice is generally regarded to be just that, the practice of states, not international organizations or other actors. (152) The acts of international organizations have also been suggested as sources of evidence of customary international law. (153) Setting aside the question of whether a given entity is or is not a state, which is yet another mixed question of induction and deduction, law and politics, the question that sometimes arises is which actors within a state are capable of manifesting state practice. (154) Some authorities have argued that decisions of courts do not qualify as state practice since courts cannot bind the state, e.g. as under a treaty, under international law. (155) Others have argued that any act attributable to a state, e.g. under the Draft Articles on State Responsibility, can constitute state practice, and even acts that are not attributable could still constitute state practice where they are adopted by the state. (156) This rule is yet another deductive step. An alternative could be drawing an analogy with the Vienna Convention on the Law of Treaties prescribing those actors that have the capacity to bind the state. (157) This analogy, however, when compared to the wider scope of actors usually considered in customary international law analysis (e.g. acts of courts), also suffers from the weakness of probably being too narrow. Any analogy drawn, though, would be a deductive exercise. The Draft Articles was largely a codification, and thus presumably an inductive, exercise, (158) but drawing an analogy between the Draft Articles rules on attribution (themselves based on customary international law) to determine the rules on the formation of customary international law is a deductive step. The question could be approached inductively, perhaps with the same outcome, but courts usually reach this rule by deducing the requirement from either or both of the ICJ Statute language or postulates about the nature of the international legal system (e.g. "states are the only subjects of international law" etc.). This is not to say that this is incorrect, but merely that it is deductive.

    2. Qualifying Categories of Acts

      Second, courts approach the question of which acts can constitute evidence of state practice and opinio juris by identifying categories of acts that are suitable as evidence of customary international law and, implicitly, those that are not. This must be distinguished from the later step where the actual evidence before the court is assessed as reliable and probative of a rule or not. (159) This preliminary step involves the building of a threshold classification system for types of evidence that might be submitted.

      Various courts and tribunals, the International Law Commission (ILC), and certain scholars, notably Brownlie, have reached conclusions on possible categories of state acts that are suitable for proving the existence of a rule of customary international law. These categories include the existence of a multilateral convention on point where the convention records, defines or develops customary international law; (160) the existence of claims to rules of customary international law before national courts and the judgments or other reactions of courts when decided on issues of customary international law; (161) domestic legislation of states on issues governed by customary international law; (162) public acts or statements made to the international community (163) (either in the context of the work of the ILC (164) or in treaty negotiations (165)); the conclusions (he they Draft Articles or otherwise) of the ILC; (166) and the teachings of publicists. (167) What can be controversial for each category is whether or not that category of acts is evidentiary of the way states actually act (168) or the opinions they hold. (169)

      One difficulty with this step is that the process of establishing linguistic categories is always one of necessarily abstracting away from actual phenomena in order to better understand it. (170) For example, we might determine that "statements" made dining treaty negotiations could qualify as evidence of state practice, opinio juris, or both, but that language category by itself is meaningless when separated from actual instances where communications are made. We must already have a notion of what a statement is, derived from examples of statements made in the past, that serves as the basis for the abstraction of statements generally. Once the category is made based on some predetermined ideal statement, then other communications are tested against the category to determine whether they qualify for inclusion or not. This could he achieved through an inductive step, but the ILC discussion on the forms of customary international law suggests that it is; however, the ILC does not appear to have applied an inductive approach in reaching its conclusion on the categories of evidence. (171) Nonetheless, those categories appear to have been adopted by most authorities.

      A further difficulty with establishing categories is that they are abstractions of various manifestations of behavior formed by identifying certain commonalities amongst them that hold the group together as a category suitable for abstraction, but does not necessarily contemplate all commonalities. Thus these abstractions do not describe outlier events very well. (172) For example, it has been argued that a belief in the compelling nature of a practice must be "articulated" by (he acting state in order to qualify as opinio juris. (173) The reason for this argument is that the opinio juris we look for is not the state's subjective beliefs but objective behavior evidencing subjective beliefs, which must be manifested in order to be objectively interpreted. (174) This author disagrees with that articulation, in the sense that writing or speech, is necessary. A subjective belief need not be expressed objectively in writing or speech in order for us to attempt to objectively understand it. Writing or speech simply makes it easier to evidence and understand the belief objectively. For example, we have always accepted acquiescence as evidence of the formation of a custom, and acquiescence is, generally, understood to be an omission. (175) The ILA has suggested that all of the eligible acts must be "public" in the sense of having been communicated to at least one other state to provide an opportunity for reaction (176) and that omissions can constitute practice. (177)

      In any event it is unclear whether there could be any agreement on the descriptive homogenization of all volitional manifestations into these prescriptive categories leading to an understanding of the state's practice. (178) This problem is partly due to the differences in the contemporary and historical assessment of the meaning of certain acts, (179) the difficulty of the abstraction of the mind of the state (180) and the difficulty of the distinction between political positions of state organs and the "beliefs of state." (181) In addition, it is not clear that states always consider existing or forming customary international law when they act or that they truly engage in an offer-acceptance discussion. (182)

      By way of example of the often deductive nature of selecting categories of acts, we can again consider the ILC's draft articles on state responsibility, specifically the portion on attribution. Here we get an example of how the ILC views the evidence of customary international law. Most of the evidence of the rule of attribution constitutes cases of international courts or arbitral tribunals (and in one case a special commission, not a court or tribunal in the usual sense (183)), which might or might not truly evidence state practice. (184) These items of evidence constitute subsidiary or persuasive sources of the law at best. However, if the ILC truly wanted to undertake an inductive approach with these subsidiary sources, it would have had to take the next step, which is to examine the cited cases to determine if they were decided following inductive study. Otherwise, the ILC would be conducting an inductive study of deductive studies. Continuing with the theme of subsidiary sources, the ILC also cited a few jurists, though this was relied on considerably less than case law, though the same concerns as with case law apply here. (185) In addition, the ILC referred to several treaty provisions when examining the issue of attribution, apparently applying a deductive methodology. (186) On the other hand, the ILC did, on a few select occasions, cite to domestic cases, legislation, and statements of states either outside or within international organizations, which would be inductive examination of non-subsidiary evidence of customary international law. (187) However, in some of those cases, the ILC admitted to citing them for their conclusions on immunity, not attribution, which could then inform the conclusion on attribution by deductive analogy. (188) In sum, this ILC analysis mixes inductive and deductive analysis in establishing its categories of acts that are eligible for study.

    3. Quality of the Acts: Density, Uniformity, Consistency, Extensitivity, and Representativity

      In addition to requiring evidence of...

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