One can even set up quite ridiculous cases. A cat is penned up in a steel chamber, along with the following diabolical device (which must be secured against direct interference by the cat): in a Geiger counter there is a tiny bit of radioactive substance, so small, that perhaps in the course of one hour one of the atoms decays, but also, with equal probability, perhaps none; if it happens, the counter tube discharges and through a relay releases a hammer which shatters a small flask of hydrocyanic acid. If one has left this entire system to itself for an hour, one would say that the cat still lives if meanwhile no atom has decayed. The first atomic decay would have poisoned it. The ψ-function of the entire system would express this by having in it the living and the dead cat (pardon the expression) mixed or smeared out in equal parts.
1 Introduction
Normative efforts in international law – including interpretation – must be grounded on a sound ascertainment of the sources of legal obligation. What might appear as a comforting truism for followers of black letter law seems an almost unattainable quest when it comes to the identification of international custom. This chapter proposes a pragmatic positivist approach to the identification of non-consensual, unwritten law: Schrödinger’s custom. If the classic textbook ‘two-element’ theory of customary international law (CIL) is valid – and the ILC still seems to think it isFootnote 2 – then at least half of the identification process consists of an empirical assessment. It requires to look at – to follow the title of Louis Henkin’s seminal workFootnote 3 – how nations behave. Under the classical view of realism, states act according to a set of inherent interests. These may provide a compass for orientation through the haze of normative propositions. The chapter begins by characterising CIL among the sources from which international rights and obligations arise (Section 2). It then moves on to depict the process of identification referred to here as Schrödinger’s custom including its implications for the issue of custom interpretation (Section 3). On that basis, it discusses how international relations theory may help predict the outcome of the identification process (Section 4). A conclusion rounds it all off. (Section 5).
2 Custom as a Source of Legal Obligation
If one accepts the catalogue of manifestations of international law in Article 38(1)(a)–(c) of the Statute of the International Court of Justice as an expression of universal state consensus,Footnote 4 one must look for ‘international custom, as evidence of a general practice accepted as law’. Without overthinking the implications of the wording referring to custom as the evidence as opposed to being evidenced by ‘a general practice accepted as law’,Footnote 5 one could simply take the provision at face value: references to custom as a source of legal obligation imply the existence of evidence as to ‘a general practice accepted as law’. Invocation of custom proposes the possibility of identifying both state practice and opinio juris, making ‘international custom’ and ‘evidence of a general practice accepted as law’ synonymous sides of an equation.Footnote 6 In this view, ‘international custom’ comprises both the process of identification (Rechtserkenntnis) and the underlying acts of law creation (Rechtserzeugung).Footnote 7
How may these underlying acts be characterised? The element of ‘practice’ reaches directly into international relations as they are conducted on a daily basis. In addition, for something to constitute custom, the respective behaviour must follow a sense of legal obligation. This has led certain strands in the literature to equate custom with tacit agreements.Footnote 8 Yet the general principles of law ut res magis valeat quam pereatFootnote 9 and favor contractusFootnote 10 carry the assumption that states adopting Article 38 of the Statute of the International Court of Justice intended to give meaning to its words. That custom is unwritten, unless it is codified, seems uncontested. But following ‘international conventions, whether general or particular, establishing rules expressly recognized’, ‘a general practice accepted as law’ must also mean something other than a consensual agreement. Unless one were to stretch the word ‘convention’ beyond its ordinary meaning under international law (for the lay use of the term might actually be synonymous with custom), Article 38(1)(a) refers to ‘agreements’. As such, these may be written or unwritten, even implicit in the form of a tacit agreement.Footnote 11 When the Statute of the International Court of Justice requires that they establish ‘rules expressly recognized by the contesting states’, this refers to the express recognition inherent in the process of reaching an ‘agreement’.
If one were now to equate ‘a general practice’ with ‘international conventions, whether general or particular’ and ‘accepted as law’ with ‘establishing rules expressly recognized’, no sense would be given to the two separate provisions included in Article 38(1) of the Statute of the International Court of Justice. In short, opinio juris cannot simply be equated to an oral or tacit agreement. Still, it represents a quasi-consensual element, in that states could equally choose to answer the question ‘did you just behave that way because you thought there is a legal obligation to do so’ negatively.Footnote 12
3 Identification
The state of CIL is in constant flux. The paradox that a customary norm must first be broken in order for a new one to arise, follows the Linnaean urge of scholars to sort and categorise their surroundings. But this approach does not do justice to the dynamic nature of a set of norms that is largely dependent upon the interaction of states.Footnote 13 While an awareness of certain trends within a particular area of law is both useful and necessary to satisfy expectations towards the rule of law, a full assessment is only necessary once a specific argument is put forward. Like a snapshot photograph, CIL is identified at a certain point in time, be it within judicial proceedings or in a scholarly publication.Footnote 14 Since custom implies both identification and creation, their temporal dimensions collapse. The view that CIL is made in the past becomes a myth.Footnote 15
Custom forms only in the present, once it is invoked and an observer is introduced. Explanatory aid may be sought from the famous thought experiment of Austrian physicist Erwin Schrödinger.Footnote 16 In his (for pet lovers luckily only theoretical) experimental set-up, a cat is placed in a steel chamber together with a vial of deadly acid that is released the moment an atom from a piece of radioactive material decays. However, it is equally probable that the radioactive material does not decay. Without an observer, there is no knowing whether the atom has decayed. Until that point in time, both the living and the dead cat must be assumed to exist. They are ‘mixed or smeared’ together.Footnote 17 What Schrödinger intended as an illustration of the paradox between reality and theoretical quantum-mechanics may easily be transposed to the problem of CIL formation. Until an observer is introduced, it is unclear how many states have already engaged in practice accompanied by opinio juris.
This should not be mistaken with the identification of an exact point in time at which a particular norm of CIL was created. The question is only as to the present existence of ‘evidence of a general practice accepted as law’. As Maurice Mendelson pointedly illustrated,
it makes no more sense to ask a member of a customary law society ‘Exactly how many of you have to participate in such-and-such a practice for it to become law’ than it would to approach a group of skinheads in the centre of The Hague and ask them, ‘How many of you had to start wearing a particular type of trousers for it to become the fashion – and, indeed, de rigeur – for members of your group?’ … The customary process is in fact a continuous one, which does not stop when the rule has emerged, even if one could identify that exact moment. To illustrate the point, I would like to introduce a simile. … My simile is the building of a house. It is often not easy or even possible to say exactly when a house has been created. Clearly, it is not when the first foundation stone is laid. But it is not when the last lick of paint has been added either. It is problematic at exactly what point we could say ‘This is a house’. Do we have to wait for the roof to go on, for the windows to be put in, or for all of the utilities to be installed? So it is with customary international law.Footnote 18
Rather than the point of formation, the observer will ‘take a still photograph, so to speak, of the state of the (customary) law at a given moment’,Footnote 19 the lex lata. The relevant question in practice – and in scholarship, for that matter – will mostly be the application of a certain rule to a particular set of circumstances, rather than a historic narrative of when and how a rule has formed.Footnote 20 In Charles De Visscher’s words, ‘[i]n international relations more than elsewhere, the fact precedes its classification’.Footnote 21 The result is simply a manifestation of the dynamic character of international relations.
In our experiment, what do we imagine this observer to look like? Obviously, it cannot be a lobbyist or policymaker, nor an idealist international lawyer.Footnote 22 So, should it be a judicial robot, an algorithm fed with empirical data? While this idea of an objective assessment seems attractive at first, it is hard to see how this would deliver equitable results; more likely, such a sterile approach to law identification – which ultimately relies on the interaction of states as raw data – might result in a ‘Bizarro World’ image of international law. The fact that states torture with the conviction that they have a legitimate basis for doing so – one must only think of the ‘ticking time bomb’ scenarioFootnote 23 – would result in a permissive rule allowing torture under such circumstances.
The analysis requires an underlying human corrective. It is in the same sense that Andreas Paulus and Bruno Simma speak of the need for an ‘enlightened positivism’.Footnote 24 It would seem fitting to rely on the proverbial man on the Clapham omnibus. This reasonable – we might also imagine ‘extra-terrestrial’ – is neither an idealist, nor a cynic, neither a revisionist, nor an innovator. As little is he driven by a particular national interest, as by the ideal of the international community as a civitas maxima. Admittedly, this is a ‘you know it, when you see it’ approach, but in combination with the identification of CIL restricted to a certain point in time it will surely allow for a more grounded assessment of the body of CIL than any elaborate game theory model or natural law-based impulse. Occam’s razor will easily help in the identification of state practice and opinio juris.Footnote 25
What does this imply for the act of interpretation? If the temporal dimensions of creation and identification collapse, it can only result in ‘instant interpretation’. As custom is frozen in the moment of its invocation, any statement about its future application becomes meaningless. Instead, custom must be repeatedly reassessed, unless there is a good faith assumption that the original invocation still constitutes ‘evidence of a general practice accepted as law’. Any subsequent practice always paves the road towards new custom. Taking the example of a codification, if one were to ‘interpret’ its content for purposes of clarification, one would either be interpreting ‘subsidiary means for the determination of rules of law’Footnote 26 to help identify such ‘international custom, as evidence of a general practice accepted as law’,Footnote 27 or again engage in the identification of the underlying acts of law creation, thereby acting as an observer to ‘Schrödinger’s custom’.
4 State Interest
Are the implications of this mode of identification on the interpretation of CIL that it simply becomes unpredictable? As Malcolm Shaw writes, ‘[c]hange is rarely smooth but rather spasmodic’.Footnote 28 If state practice follows day-to-day world affairs, international relations theory might help. As Louis Henkin convincingly laid out in his seminal work How Nations Behave, states act according to carefully calculated interests and dependent upon the consequences of their conformity to or violation of international law.Footnote 29 This approach is, generally, quite similar to the economic theory of negligence that ‘[w]hen the cost of accidents is less than the cost of prevention, a rational profit-maximizing enterprise will pay tort judgments to the accident victims rather than incur the larger cost of avoiding liability’.Footnote 30
The term ‘interest’ derives from the Latin interesse, which carries the meaning ‘to differ’ or ‘to make a difference’. The interest is something that makes a difference to someone – or, if speaking of a juridical entity, to something. In discussing these issues, one is always confronted with the problem of anthropomorphising states.Footnote 31 Some writers have gone as far as to argue that states are not capable of holding such interests, ‘as if artificial entities could have discernible motivations’.Footnote 32 However, this position overlooks the idea of statehood as represented through the collective of individual actors with a common agenda. Just as what makes a difference for an individual employee does not necessarily make a difference for a corporation, it does not necessarily make a difference for a state.Footnote 33 Each entity, the natural person as well as the juridical body, carries distinct goals and purposes. Some may correlate, some may differ. It is the nature of the respective actor that determines the interest.
The expression ‘state interest’ or ‘national interest’,Footnote 34 as it is sometimes found in the literature, confers the idea that there must be a common set of factors that are important to the existence of the abstract entity of the state. At the same time, it has been suggested that ‘no agreement can be reached about its ultimate meaning’.Footnote 35 Still, it seems to be an important factor in decision-making of political stakeholders,Footnote 36 best reflected in the anecdotal quotes of Charles De Gaulle and Henry Kissinger that their respective states had ‘no friends’ but ‘only interests’. That states ultimately strengthen and enrich themselves at the cost of others cannot shock an international lawyer since Emer de Vattel’s 1758 publication of Le Droit des Gens.Footnote 37
The idea that law formation follows the interplay of interests is also not particularly new. Carl Schmitt – the Dooyeweerd of German peopleFootnote 38 – already argued that public international law in the nineteenth century rested less on ideas of sovereignty than on a selection of specific state interests.Footnote 39 Jean d’Aspremont found that ‘[e]ven liberals and constitutionalists agree that States first strive to promote their own interests’ and that ‘they naturally act to maximize the interest of their constituency given their perception of the interests of other States and the distribution of State power’.Footnote 40 Martti Koskenniemi has called reference to this fact a ‘truism, present since Vattel’.Footnote 41 Richard Steinberg convincingly showed how different schools of international legal thought and international relations theory resorted to realism whenever they dealt with states.Footnote 42 Today, Martin Dixon begins his introductory textbook on international law by finding that ‘[i]t is true of all legal systems that vital interests of its subjects may prevail over the dictates of the law’.Footnote 43 According to Malcolm Shaw, the motivation behind an act of a state lies within the way in which ‘it perceives its interests’, which again depends upon ‘the power and role of the State and its international standing’.Footnote 44
What are these supposed interests that determine the probability of state action? For any realist, states are driven by two principal considerations: first, national security, comprising the protection of statehood, territorial integrity, as well as sovereignty, and, second, a functioning economy. Gerhard Hafner identified five traditional areas of state interest: ‘the protection of statehood, territorial integrity, sovereignty, security and economic wealth’.Footnote 45 Nicholas Onuf speaks, in the Hobbesian tradition, of ‘standing, security, and wealth’.Footnote 46 Recalling the definition of what constitutes a state, these ‘traditional’ interests are inextricably linked to its ‘survival’.Footnote 47 Each student of international law knows that the ‘primary subjects’Footnote 48 of international law consist of a permanent population, a defined territory and a government.Footnote 49 Recalling this definition, these ‘traditional’ interests are inextricably linked to the ‘survival’ of a state. In a sense, to anthropomorphise states once more, this feature is not so different from the ‘survival instinct’ of individuals. The latter are equally interested in escaping the Hobbesian bellum omnium contra omnes before all else. The social contract that allows for this escape wants to be upheld. Thereby, state interest is equated with the survival of the state.Footnote 50 Without territory, without governmental control, it lacks its constitutive elements.
While states require individuals to take action on their behalf, these ‘do not act on their own account but as State officials, as the tools of the structures to which they belong’,Footnote 51 a view that is further reflected in the rules of attribution in the International Law Commission’s Articles on State Responsibility.Footnote 52 The state organs are limited by the framework that is the respective state, even if this is little more than the collectivity of individual decisions. Its economy, social structure, and cultural heritage will largely determine what is opportune. Thus, states may weigh their interests differently and in accordance with additional factors such as ideology, be it liberal democracy, socialism, or some pan-territorial or ethnic component.Footnote 53 Still, the definition of the state is tainted by the fact that individuals act on its behalf. The way it is externally perceived is shaped by its successive governments. Therefore, it is important to differentiate between the state, its organs, and its population in making any determinations as to its character. Brierly defined the state exactly along these lines as ‘a system of relations which men establish among themselves as a means of securing certain objects, of which the most fundamental is a system of order within which their activities can be carried on’. At the same time, he cautioned that the state ‘should not be confused with the whole community of persons living on its territory’, as ‘it is only one among a multitude of other institutions, such as churches and corporations, which a community established for securing different objects’.Footnote 54 Yet this is little different from the way that multi- or transnational corporations such as Walmart, Royal Dutch Shell, or ExxonMobil are perceived against the background of a change in the board of directors. Only in extreme situations such as a revolution, is it likely that states entirely change their character on the initiative of a government or other persons or groups of persons exercising authority. States, as all other legal entities, are fictions to express the idea that individuals may come together to create an entity that pursues goals not necessarily representing their own and vice-versa. Even Immanuel Kant, one of those authors most championed for the cause of lofty values, pointed out that the wellbeing of the state – the ‘Heil des Staates’ – does not necessarily correspond with the wellbeing or happiness of its respective citizens.Footnote 55
A number of structural arguments have been brought against this view. For example, the need of states ‘to include [NGOs] in their foreign policy analysis and respect their interests in the process of creating norms of international law’ as a result of ‘the power exercised by them through the use of media and similar means’.Footnote 56 However, these are means to an end:Footnote 57 the survival of states and, in this case, governments. These will likely set acts in the name of a state that aim at preventing civil unrest, cultivating a happy electorate,Footnote 58 attracting investment and highly skilled labour, securing development aid, gaining admission to an international organisation – the list goes on.Footnote 59 There is also still a certain impetus of morality determining action in the face of mass human rights violations or unrestrained warfare.Footnote 60 But this altruistic impulse seems often by itself too weak to spur any form of meaningful intervention.Footnote 61 Notwithstanding, the constitutionalist or Kantian argument still stands strong within international legal scholarship, spurred by Wolffian ideas of a civitas maxima.Footnote 62 Its moral superiority is, after all, compelling.Footnote 63 Equally, state interest is not a one-way street. Interests of other states must be taken into account at some level, in particular in an international relations reality that has become dominated by a universal international organisation that is the United Nations.Footnote 64 Yet, this is a simple outcome of the discourse within which international relations take place,Footnote 65 already identified and incorporated by structural realism.Footnote 66 Yet ‘subsidiary interests’ will not necessarily predict what states will do, when competing core interests of survival arise. In such cases, states will usually resort to ‘Realpolitik’.Footnote 67 They will, generally, not compromise on their interests out of altruistic motives – in this case vis-à-vis states – or out of concern for public opinion.Footnote 68 Even Gerhard Hafner, who takes a position that emphasises the role of the individual in international law, concedes that states take all the weight in this balance of interests when he writes that ‘the reflection of the – nevertheless increasing – individual-oriented interests in norms of international law still depends on the will of states’.Footnote 69
Equally, the constitutionalist argument does not stand empirical scrutiny. Just as states will bulldoze over public image considerations, whenever their survival interests are at stake, states will limit their activism with regard to jus cogens and erga omnes obligations to situations in which their own interests are concerned.Footnote 70 In the competition of ‘first-order reasons’, to borrow Joseph Raz’s terminology,Footnote 71 interests related to the survival of the states will, naturally, prevail. In absence of an exclusionary rule, a state will balance these interests in accordance with their respective ‘strength’ or ‘weight’.Footnote 72 A ready example is the primacy that states accord to national security considerations over basic citizens’ rights in the face of terrorism.Footnote 73 Altruistic obligations, in particular, do not seem likely candidates for custom.
How can these considerations on state interest help identify possible trends in CIL? Add to this effectivity and reciprocity, the catalysers of international law formation,Footnote 74 as the vertical and horizontal angles for the realist’s theodolite and a credible prediction should be the likely result. After all, it is not just international law that guides the behaviour of states, but politics of interest. In turn, interest determines the formation of international law.Footnote 75 There might also exist areas of law in which compliance is not necessarily rewarded by reciprocal behaviour, but it seems that CIL will, at least, likely reflect an equilibrium of interests.Footnote 76
5 Outlook
The ‘cliché’Footnote 77 two-element theory of CIL can provide a simple solution against the legion of alternative theories. As a manifestation of international law that does not directly spring from the ‘will’ or ‘consent’ of states, it reflects their perpetual international relations. States do not voluntarily form a will at the international level but consciously or unconsciously influence its creation through their actions. Following the metaphor of ‘Schrödinger’s custom’, until an observer is introduced to determine what the particular customary rule is in a certain moment, CIL remains ‘mixed or smeared’.
Once an observer is introduced and the temporal dimensions of creation and identification collapse, ‘interpretation’ can only mean the assessment of ‘evidence of a general practice accepted as law’ at a certain point in time. Subsequent practice will always only ever pave the road towards new custom.
This should not suggest a nihilistic view of custom. While the literature may already now concede the instructive value of realism when dealing with states, stronger attention should be given to the interplay of this ‘truism’ with the formation of CIL. It is obvious that parties bring their interests to the table when negotiating a treaty. Strangely, it appears less obvious whenever scholars seek to harness custom for the normative project of international law. More even than other sources, CIL will most likely reflect an equilibrium of interests.
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