The Neglected Potentials of Vagueness and Ambiguity in International Law

Striving for clarity is one of the central tasks of a lawyer, at least so common wisdom tells. Whether lawyers interpret a statute, try to discern the ratio decidenci of a court judgment or seek to identify a norm of international custom, they look for a clear-cut, ideally brief and easily comprehensible underlying rule or principle, ratio or general logic that will present the solution to the legal question at hand. Legal certainty and predictability play a central role in creating, developing and preserving both domestic and international legal orders or regimes.1 Clarity is their prerequisite. And yet, law hinges upon language2 – and language often is not clear, but the opposite, i.e. either vague or ambiguous. If I say “The sentence was unconscionably long”, by using the word ‘sentence’ I may refer either to a linguistic unit or to a period of incarceration.3 Moreover, what constitutes a ‘long’ sentence (under both meanings) is far from clear in this example. Vague is also the qualifier ‘unconscionably’ and taking the entire sentence, both as the combination of these separately ambiguous and vague terms and as an entity, further adds to the confusion.
As for the distinction of vagueness and ambiguity (VaA), albeit definitions differ,4 I will understand them as different levels of lack of clarity:5 Ambiguity pertains to discreteness whereas vagueness pertains to fuzziness. Applied to the above example “The sentence was unconscionably long”, ‘sentence’ has two discrete meanings – a linguistic union or a period of incarceration – and is hence ambiguous while ‘long’ and ‘unconscionably’ lack such discreteness and are thus vague.6

An Analytical Framework for Vagueness and Ambiguity in International Law
Many (international) lawyers perceive that their job is to dispel confusion caused by VaA by the means of interpretation and therefore mostly look at VaA as something to be resolved: VaA poses a problem finding the solution to which appears a lawyer’s primary task. I submit in this blog post that this view misses central aspects of the inevitable consequences of the fact that language, as the instrument of (international) lawyers, is vague and ambiguous. Instead of dismissing VaA exclusively as a problem, it should be acknowledged that it can also be, among others, an opportunity. Therefore, so I contend, international legal thinking about the interpretation of international legal norms requires an analytical framework for VaA in order to understand, explain and assess central phenomena and characteristics of international law. While I identify five categories of VaA constructing such analytical framework – manifestations, actors, forms, functions and aspects of VaA7 – here, I would like to focus on how VaA manifest themselves (manifestations), who is involved in such manifestations (actors) and, centrally, which consequences does this have for the aspects of VaA, in particular VaA as opportunity.
There are two manifestations of VaA, VaA production and VaA reception. VaA is being produced constantly. Lessons from hermeneutics and linguistics8 tell us that literally any use of language may produce VaA. Such VaA production can be deliberate, i.e. strategic, or inadvertent, i.e. non-strategic. Non-strategic VaA production is the most common occurrence, e.g. the definition of a term in a United Nations Security Council (‘UNSC’) Resolution laying out sanctions against a recalcitrant state. If, for example, the definition of ‘chemical weapons’ remains ambiguous or even vague, this may seriously undermine the effect of the sanction. On the other hand, the same Resolution may deliberately remain vague and/or ambiguous in order to: (a) reach a consensus among the required majority of the Security Council Members, including particularly the P 59; and (b) at the same time allow for as much leeway of interpretation that some Members may pursue a goal that other Members sought to prevent, while not going beyond what the language of the resolution permits.
The second manifestation represents VaA reception. If interpretation is at least as much about the audience’s understanding of a word, phrase, etc. as it is about the speaker’s intention,10 then the VaA reception is pivotal. As with VaA production, VaA reception can be strategic and non-strategic. The most obvious form of strategic VaA reception is (the attempt) to reduce VaA, e.g. by way of correction or amendment, or – if the means of correction or amendment are not (realistically) available, as would usually be the case with international treaties, for example – by way of interpretation. However, the audience of an act, treaty, etc. may also inadvertently misunderstand such act, treaty etc., which eventually leads again to VaA production.

From Problem to Opportunity
International law provides a myriad of actors that produce and receive VaA, which are either authors or audience of such VaA production and/or reception. One of the central of such actors whose importance has been constantly increasing in recent decades are international judicial bodies, who are tasked with interpreting international law and thus dealing with VaA. A decision by an international court of tribunal is meant to resolve a dispute that often arises over the meaning of a specific treaty clause, customary norm etc. and thereby intends to reduce vagueness and/or ambiguity. But such judgment also enjoys international normativity and thus is of a considerable law-making nature – among the disputing parties but usually also beyond.11 In this context, the aspect of VaA as opportunity is particularly instructive with respect to international adjudication and the international judicial function. VaA as opportunity enables judicial actors to choose from a variety of possible meanings or understandings of a legal norm or concept and thus puts them in a position to exercise a variety of judicial functions beyond mere settlement of the dispute at hand. International courts and tribunals may thereby take on the role of law- or policy-makers and thereby serve further-reaching functions such as the promotion of the international rule of law, the constitutionalization of international law, the furtherance of democracy on the domestic and international level, or merely the politics of its own role within a treaty regime or the international community at large.12 In other words, VaA (as opportunity) becomes a central instrument of global governance by international adjudication.
Morevoer, strategic VaA production provides an opportunity in the field of international law-making by party consensus. In the context of international negotiations on the adoption of treaties, resolutions, etc., ‘constructive ambiguity’ describes the phenomenon of negotiators deliberately – i.e. usually deliberately on all sides of the negotiation table – inserting terms and phrases into the respective document that blur the meaning of the text in order to build consensus by getting all sides to commit to a final document that allows for everybody to ascribe it a meaning suitable for his or her purposes. Within the terminology posited here, both ambiguity and vagueness may be constructed (and constructive) in the way described. What are the benefits of this strategy? The problems entailing VaA are obvious and potentially disastrous: imagine, e.g., an armistice treaty that does not clearly define the front lines. On the other hand, often – and particularly if the question of war and peace is at stake – reaching an agreement is better than none at all, whatever its flaws. In this vein, VaA represent the solution to negotiation deadlock. Further, constructive ambiguity or vagueness make it possible for both sides to claim victory at the negotiation table without having to determine the victor in actual military confrontation.

My central aim in this post was to illustrate the underestimated and under-scrutinized aspect of VaA as opportunity in interpreting international law, including the role of VaA manifestations (production and reception) vis-à-vis international adjudication and international law-making. While this post could only give a glimpse on the matter, which I will soon elaborate on in more detail elsewhere,13 I contend that international legal thinking on interpretation remains incomplete until it embraces that VaA has more to offer than just being an obscurity that has to be resolved.


1. See Jean-François Gerkens, Legal Certainty v Legal Precision – Some Thoughts on Comparative Law, Fundamina 16  (2010), 121.

2. On the use of language in international law generally see Philip Allott’s still unrivalled 1971 piece in the British Yearbook of International Law: P. Allott, ‘Language, Method and the Nature of International Law,’ British Yearbook of International Law 45 (1971), 79.

3. The example is taken from J. Anderson, ‘Misreading like a Lawyer: Cognitive Bias in Statutory Interpretation,’ Harvard Law Review 127 (2014), 1521, 1535.

4. Cf., e.g., M. Thaler, Mehrdeutigkeit und juristische Auslegung (Springer 1982), 2; see also J. Kammerhofer, Uncertainty in International Law (Routledge 2011), 118.

5. Cf. also R. Poscher, ‘Ambiguity and Vagueness in Legal Interpretation,’ in L. M. Solan and Peter M. Tiersma (eds.), Oxford Handbook of Language and Law (OUP 2012), 128, 129.

6. See Anderson (supra, note 3), 1535.

7. For a more comprehensive study into this subject see my forthcoming piece in Vol. 59 of the German Yearbook of International Law: A. Kulick, From Problem to Opportunity?: An Analytical Framework for Vagueness and Ambiguity in International Law, 59 GYbIL 2016 (forthcoming), draft available at

8. See only H.-G. Gadamer, Truth and Method (Continuum, 2nd rev. ed., 1989), pp. 130 et seq.; T.  Endicott, Vagueness in Law (OUP 2000), 7-29; A. Bianchi, ‘Textual Interpretation (International) Law Reading: the Myth of (In)determinacy and the Genealogy of Meaning,’ in P. Bekker, R. Dolzer and M. Waibel (eds.), Making Transnational Law Work in the Global Economy – Essays in Honour of Detlev Vagts (CUP 2010), 34 et seq.

9. See only M.N. Shaw, International Law (CUP, 7th ed., 2014), 877-879.

10. See only D. Peat and M. Windsor, ‘Playing the Game of Interpretation: Meaning and Metaphor in International Law,’ in A. Bianchi, D. Peat and M. Windsor (eds.), Interpretation in International Law (OUP 2015), 3.

11. Gleider Hernández notes how uncontentious this notion is these days, citing to such different authors as the likes of Dworkin, Kelsen and Lauterpacht, see G. Hernández, The International Court of Justice and the Judicial Function (OUP 2014), 87-93.

12. On these various judicial functions see Karen Alter, The New Terrain of International Law – Courts, Politics, Rights (2014), 9 et seq. On democratic legitimacy and international adjudication see generally A. von Bogdandy and I. Venzke, In Whose Name? – A Public Law Theory of International Adjudication (OUP 2014).

13. See Kulick (supra, note 7).

This LawLog post summarizes some central ideas of Andreas Kulick’s article “From Problem to Opportunity?: An Analytical Framework for Vagueness and Ambiguity in International Law”, which is forthcoming in the German Yearbook of International Law Vol. 59 (2016). Access to a draft version of the article is available on SSRN.

Written by

Andreas Kulick is Assistant Professor (wissenschaftlicher Assistent) at the University of Tübingen. He was a Visiting Researcher at the WZB Center for Global Constitutionalism in January and February 2017.
Website at the University of Tübingen

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