Erga Omnes Obligations as Rules of Customary International Law

The notion by the Court in the Barcelona Traction dictum that erga omnes obligations may derive from “general international law - - [or] international instruments of a universal or quasi-universal character” has understandably led to confusion on the sources of erga omnes.

However, the fact that the Barcelona Traction decision was not based on any particular treaty but on general rules on the treatment of aliens and their distinction from erga omnes rules, as well as ICJ jurisprudence on the matter in overall, show that Court refers to erga omnes obligations as customary rules.²⁴⁹ Customary obligations may of course be, and often are, also recognized in treaty law, which however serves as a further evidence of their acceptance as general international law.²⁵⁰ General international law, on the other hand, applies in prin-ciple to all States. Custom is thus less consensual than treaties, and “cannot therefore be the

248 Final report of the Working Group, p. 11, para. 31. See Article 31(1) of the VCLT on “object and purpose”

interpretation.

249 Tams 2005, p. 122–123.

250 Ibid., p. 123. See also North Sea Continental Shelf (Federal Republic of Germany v. Netherlands; Federal Republic of Germany v. Denmark), ICJ Reports 1969, p. 41, para. 71, stating that Article 6 of the 1958 Geneva

subject of any right of unilateral exclusion”,²⁵¹ bearing in mind that States may effectively oppose to a certain rule of customary law.²⁵²

Although erga omnes obligations are usually conceptualized as deriving from custom, if the possibility of jus cogens norms deriving from “general principles recognized as law” is ac-cepted,²⁵³ also these principles have erga omnes effect, since jus cogens are necessarily erga omnes.²⁵⁴ However, since the theory of general principles is still undeveloped, and the source is rarely applied in international law, this master’s thesis will focus on customary erga om-nes. This requires defining what custom is and how it emerges.

Article 38(1)(b) of the ICJ Statute states that the Court shall apply, inter alia, “international custom, as evidence of a general practice accepted as law” when deciding on a dispute sub-mitted to it. It was further recognized by the Court in Continental Shelf Case, that “- - the material of customary international law is to be looked for primarily in the actual practice and opinio juris of States”.²⁵⁵ Thus, customary international law is understood to be formed by two elements: state practice and opinio juris of States. Making these generalizations should involve evaluation of whether the practice is fit to be accepted and is in truth generally accepted as law.²⁵⁶

Convention had “since passed into the general corpus of international law, and is now accepted as such by the opinio juris, so as to have become binding even for countries which have never, and do not, become parties to the Convention.”

251 ICJ Reports 1969, pp. 38–39, para. 63.

252 It is usually accepted in international law that during the formation of the customary rule, State may effec-tively oppose by persistent objection of being bound by that rule, see Crawford 2012, p. 28. There is also a controversial concept know as subsequent objector, see Ibid., p. 29, but it is not possible for State alone change its mind on custom: a substantial group of States must agree, and a new rule of custom starts to form, from which States may then object from by the concept of persistent objector. It goes without saying that such process is very slow. As can be seen, there is an intrinsic tension in the concept of custom: it is less consensual than treaties in that it can bind without express consent, but consent, or “acquiescence” is required in its for-mation. As pointed out by Koskenniemi, the differentiation between custom and treaties on their consensual nature seems to leak, as treaties seem to also have at certain situations objective applicability, see Koskenniemi 2006, p. 407. However, e.g. the concept of objective regime (chapter 3.2.1) is controversial, and the general rule is that treaties do not include objective applicability. The issue, however, deserves closer scrutiny, yet cannot be discussed further in this thesis because of length restriction.

253 See chapter 3.5.1 discussing this.

254 See chapter 3.5.2.

255 Continental Shelf Case (Libyan Arab Jamahiriya v. Malta), ICJ Reports 1985, p. 13, pp. 29–30, para. 27.

256 Crawford 2012, p. 23. Custom is to be separated from mere usage (or habit). There is a certain legal obli-gation to adhere to custom, whereas usage is simply general practice or habit with no legal obliobli-gations or threat of (legal) sanctions attached to it. Usage may be, for example, ceremonial salutes at sea, i.e. international courtesy. See Ibid., p. 23–24 & Abass 2014, p. 34.

The Court has stated further requirements for the establishment of custom: uniformity, con-sistency and generality. State practice has to reach a certain limit of uniformity, and irrele-vant of the period of time that has passed, State practice – including of those States whose interests are specially affected – has to be both extensive and virtually uniform during that time period in the sense of the provisions invoked, and should show a general recognition that a rule of law or legal obligation is involved.²⁵⁷ Complete uniformity is not required, but substantial uniformity is.²⁵⁸ Further, the Court’s case law suggests that perfect consistency is not required: practice does not need to be universal for all States to be bound by it; “gen-eral” practice suffices.²⁵⁹ This means that a State is bound by international rule even if it has not itself actively participated in the practice in question or deliberately acquiesced in it:

there is no need to prove the individual consent of a State to it.²⁶⁰

State practice may consist of any action by a State or someone part of its apparatus, for example military action, official proclamations, spoken declaration by a State head or dip-lomatic protests, if the action is public.²⁶¹ However, some suggest that it may be necessary to restrict such a broad definition, for example to behaviours respecting a particular issue that amounts to direct action by – or has a direct effect on – the State whose behaviour is in question, which would leave out certain actions by State officials which do not create direct commitments to the State.²⁶².

Settled state practice must also show opinio juris, referred to as the subjective element or sometimes the “psychological element”.²⁶³ Opinio juris is the belief of a State of what it

257 ICJ Reports 1969 p.3, at p. 43, also recognized by International Law Association (ILA) 2000, p. 8, working definition n. i.

258 Crawford 2012, p. 24. The Court applied this when it refused to accept the existence of a 10-mile rule for the closing line of bays on the grounds that the practice was not substantial enough, see Anglo-Norwegian Fisheries Case (United Kingdom v. Norway), ICJ Reports 1951, p. 116, at p. 131.

259 ILA 2000, p. 24 & 8, working definition n. ii.

260 Ibid., working definition n. iii. The ILA also noted that “[t]his is also generally the position taken by States, and there have been no substantial challenges to this proposition”, see p. 24.

261 Mendelson 1999, p. 204 & ILA 2000, p. 15. However, these examples do not form the complete list of accepted actions.

262 Weisburd 2014, p. 303. Weisburd gives as an example in relation to border disputes “state representative’s vote in favor of a non-binding resolution in some international body taking a position on a border dispute to which the voting state was not a party would have no effect on that state, and would therefore not count under this definition.” The debate usually relates to UN General Assembly resolutions, as they are legally non-bind-ing for States, and States often do not vote with a view to create law, see Schwebel 1979, p. 302. However, at the same time, General Assembly resolutions are hard to ignore, at least to the extent that it may show a ma-jority opinion in issue areas of grave importance, especially if there is a clear consistency over time.

263 E.g. Crawford 2012, p. 25 & Koskenniemi 2006, p. 410.

considers to be legally mandated by international law, instead of simply by a moral obliga-tion.²⁶⁴ The role of the opinio juris seems to be that of a “sliding scale”; “[a]s the frequency and consistency of the practice decline in any series of cases, a stronger showing of an opinio juris is required.” Conversely, “a clearly demonstrated opinio juris establishes a customary rule without much (or any) affirmative showing that governments are consistently behaving in accordance with the asserted rule.”²⁶⁵ Thus, it seems, the duration of the practice does not have to be long, and for example in rules relating to airspace and continental shelf custom has emerged quite quickly.²⁶⁶ In fact, there has been academic endeavours towards a concept of instant custom for example in relation to space law²⁶⁷ or times of fundamental change in the international plane.²⁶⁸

All this may seem like forming a clear concept: all that needs to be done is showing State practice and opinio juris to determine a rule of customary international law. However, actu-ally doing this would be a “herculean task”,²⁶⁹ and it can be contested if a Court ever really goes through all relevant State practice to determine the existence of custom. This is espe-cially clear in those cases where the Court has emerged a rule as custom with what seems non-existent justifications.²⁷⁰ Even more complicated is determining the existence of opinio juris. Some writers have even suggested that the psychological element of opinio juris is not required.²⁷¹ This is partly because of the conceptual circularity of the definition of custom:

264 It was stated in North Sea Continental Shelf that settled State practice “must also be such, or be carried out in such a way, as to be evidence of a belief that this practice is rendered obligatory by the existence of a rule of law requiring it. The need for such a belief, i.e., the existence of a subjective element, is implicit in the very notion of the opinio juris sive necessitatis. The States concerned must therefore feel that they are conforming to what amounts to a legal obligation”, ICJ Reports 1969, p. 44, para. 77. A similar notion, without a reference as opinio juris (sive necessitatis) can be found in the classic PCIJ Lotus judgment, see S.S. Lotus (France v.

Turkey), PCIJ Series A, No. 10, September 7^th, 1927, p. 28.

265 Kirgis 1987, p. 149 & Crawford 2012, p. 25.

266 Crawford 2012, p. 24.

267 See e.g. Cheng 1998. Also, as worded by Cassese, "[t]hus, for instance the norm concerning the free use of outer space took shape as soon as the first spacecraft was launched“, in Cassese 1999, p. 796.

268 See e.g. Scharf 2014. However, instant does not usually mean literally instant, but “very quick” suffices, which on international plane – on which custom has traditionally taken decades if not centuries to develop – seems like an instant. The concept of instant custom, however, is somewhat controversial.

269 Bodansky 2010, p. 198.

270 For example, in Corfu Channel, the Court simply stated that “[i]t is, in the opinion of the Court, generally recognized and in accordance with international custom that States in time of peace have a right to send their warships through straits used for international navigation between two parts of the high seas without the pre-vious authorization of a coastal State, provided that the passage is innocent”, without presenting any evidence on State practice or opinio juris, see ICJ Reports 1949, p. 28.

271Crawford 2012, p. 25, footnote 29, referring to works of Paul Guggenheim and Hans Kelsen. See also Mendelson 1999, p. 292.

after all, States often act according to what they consider to be the law, thus showing opinio juris: yet the acts are therefore subsequent to existence of opinio juris, but the only way to determine the existence of opinio juris is through examination of actual State practice.

To answer this, arguments based on different stages in the development of customary rules have been laid out. As mentioned above, it may be argued that in times of fundamental change a rule of customary rule may be formalized in an “instant”, at least when combined with the reaction of other States to that event.²⁷² When such thing cannot be said to have happened, but States still consider it to be economically, politically and morally needed to act, even in contrary to international law, one may talk about opinio necessitatis, where opinio juris has only partially formed, and complete opinio juris is not required at the out-set.²⁷³ The ILA seemed to accept this line of thought when it suggested that opinio juris should be removed from the absolute criteria of formation of custom; the role of opinio juris is simply to point what practice should count towards the formation of custom,²⁷⁴ and is only sometimes required.²⁷⁵ It further stated that “[p]art of the confusion may be caused by a failure to distinguish between different stages in the life of a customary rule. Once a custom-ary rule has become established, States will naturally have a belief in its existence: but this does not necessarily prove that the subjective element needs to be present during the for-mation of the rule.”²⁷⁶

But what is the significance of these conceptual issues in a study on environmental erga omnes? First, as we next turn focus on the identification of erga omnes obligations, the iden-tification of customary rules has great significance in that relation: obligations which follow the material approach (chapter 3.4.3) need to be distinguished from “ordinary” customary

272 Cassese 1999, p. 796. In the environmental field, there is the theoretical possibility that some environmental problem evolves into a global disaster, and in that case, it can be argued that the requirement of State practice becomes completely obsolete: opinio juris emerges instant custom. This issue relates also to the topic of envi-ronmental jus cogens, which will be discussed in chapter 4.2, although this kind of speculations are not given considerable attention in this thesis.

273 Ibid., pp. 797–799.

274 ILA 2000, p. 34–35. Similar view is backed by PCIJ Lotus judgment and ICJ Nicaragua judgment, see PCIJ Ser. A, No. 10, p. 28 and ICJ Reports 1986, pp. 97–110, paras. 183–209. However, one needs to be vary when assessing the possible significance of opinio necessitates. As noted by Mendelson, “opinio necessitatis - - can play a part in the law-creating process, even though extra-legal necessity and reasonableness are not themselves sufficient to make law”, Mendelson 1999, p. 271.

275 ILA 2000, pp. 7 & 9–10. The argument of the ILA is that when the ICJ has referred to opinio juris as a necessary element of custom, the Court has done so in special situations, where the conduct is too ambiguous to constitute a precedent capable of contributing to the formation of a customary rule, or where it is necessary to distinguish practice which does not contribute, see Ibid., p. 33–35.

276 Ibid., p. 7.

rules, and if the identification of custom itself is a challenge, it must have consequences on the identification of erga omnes obligations; it thus may not be a surprise that the material approach to erga omnes is usually associated with well-known jus cogens norms. Secondly, for those obligations which are purely non-bilateralizable, deduction deems it de rigeur that the binding customary character of such obligation also means that it must be enforceable erga omnes. Thus, identification of custom is crucial. This topic is discussed in chapter 3.4.4 and extensively applied in relation to environmental erga omnes in chapter 4.3.

Thirdly, despite extensive theoretical debates, it is still the “two-element” approach of State practice and opinio juris which enjoys the recognition of States and international judicial bodies.²⁷⁷ However, it has been suggested in the ILC’s ongoing work on identification of customary international law that the weight of each element depends on the field of interna-tional law, or the type of the rule.²⁷⁸ Thus it seems, based on the above discussion, that it is somewhat justified to conclude that in the formation of pronouncedly important customary rules, such as erga omnes, the weight of opinio juris increases, and less evidence from State practice is required. However, it is still important to remember that ultimately the existence of opinio juris is also determined through practical evidence.²⁷⁹ The problem discussed above that it is hard, if not impossible, to orchestrate a thorough examination of State practice to determine the existence of an customary rule, was recognized by the ILC, and Special Rapporteur Wood discussed possibilities for making the information more readily availa-ble.²⁸⁰ Since for the purposes of the present thesis a complete review of all existing State practice would be an absurd task, chapter 4.3 will mostly focus on existing case law.

3.4 Identifying Obligations Erga Omnes