NOTES

THE HIERARCHY OF THE SOURCES OFINTERNATIONAL LAW·

By MICHAEL AKEHURSTI

Every legal system has evolved techniques for resolving conflicts between differentlegal rules. These techniques fall into three main categories.

The first technique is to make rules derived from one source prevail over rulesderived from another source; lex superior derogat inferiori.

The second technique is to make later rules prevail over earlier rules; lex posteriorderogat priori. However, this technique cannot be applied where the later rule derivesfrom a lower source than the earlier rule, unless the authority which created the earlierrule provided for the possibility of its being repealed or overridden by a later rulederived from a lower source (as when an Act of Parliament gives a Minister power torepeal parts of the Act by delegated legislation).

The third technique is to make a particular rule prevail over a general rule; lexspecialis derogat generali. (,Particular' and 'general' are relative, not absolute terms;one rule may be more general than a second rule and less general than a third rule.)But lex specialis derogat generali is no more than a rule of interpretation. In otherwords, there is a presumption that the authority laying down a general rule intended toleave room for the application of more specific rules which already existed or whichmight be created in the future, even though the specific rules might be derived froman inferior source; but this is only a presumption, which can be rebutted by proof ofcontrary intention.

All three techniques are applicable to international law, but the way in which theyare applied is slightly different. First, the hierarchy of sources is not as well establishedin international law as it is in most municipal systems. Second, the maxim lexposteriorderogat priori is sometimes difficult to apply in international law because customarylaw and general principles of law come into being gradually, so that no precise datecan be assigned to their creation. Third, the maxim lex specialis derogat generaliassumes greater importance in international law, not only because of the occasionaldifficulties of applying the other two maxims, but also because of the virtual absenceof legislation in international law. Multilateral treaties co-exist with bilateral treaties,general custom co-exists with regional and other forms of special custom, and so on.One rule of international law may be more general than another, either because it hasa broader subject-matter, or because it binds a larger number of States.- the maximlex specialis derogat generali can therefore take two different forms in international law.!

• © Dr. Michael Akehurst, 1976.I M.A., LL.B. (Cantab.), Docteur de l'Universite de Paris; Reader in Law, Keele Uni­

versity.2 A conflict between a rule binding a small group of States and a rule binding a larger group

arises only in so far as membership of the two groups overlaps. If there is no overlap, there is noconflict; a State is not bound by a rule which exists among a group of States of which it is nota member.

3 The application of the maxim can be seen in the fact that special custom prevails over general

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Article 38of the Statute of the International CourtThe Committee of Jurists which drafted the Statute of the Court in 1920 included

in their draft a provisionthat the items listed in the first paragraph of Article 38 shouldbe applied enordre successif. However,it is not clearwhether thesewords were intendedto establish a definite hierarchy of sources, or whether (as Phillimore argued) theymerely reflected the logical sequence in which the rules would occur to the judge'smind. The words en ordre successif were deleted by the Sub-Commissionof the ThirdCommitteeof the First Assembly of the League of Nations, but it is not clear whetherthe deletion was inspired by a feelingthat the idea contained in the words was wrong,or that the idea was so obviously right as not to need stating.

Some authorities have argued that Article 38 lays down a hierarchy of sources.IOthers disagree.Z

It is sometimesargued that the order in which the various items are listed in Article38 reflects the maxim lex spedalis derogat generali-eustomary rules are more generalthan treaties, and general principles of law are more general than custom.! That isoften so, but not always, as we shall see.r There is probably more truth in Le Fur'sobservationsthat treaties are easier to prove than custom and custom is easier to provethan general principles of law; that is one reason why they are likely to be applied inthat order, and perhaps why Article 38lists them in that order.!

The problem of the hierarchy of the sources of international law has seldom givenrise to difficulties in practice.sHowever, there is no guarantee that that state of affairswillcontinue; for that reason,and alsobecauseof the light which it shedson the generaltheory of international law, the topic merits further discussion.

Treaties andcustomThe Permanent Court of International Justice in severalcasesapplied treaties which

conflicted with customary rules.?However, this does not mean that treaties invariablycustom inter partes (see the discussion of special custom in the author's article on custom,above, p. 29).

However, international tribunals (with the exception of the Court of Justice of the EuropeanCommunities) have tended to apply general principles of law common to nations in general andnot general principles of law common to the parties. See International and Comparative LawQuarterly, 25 (1976), pp. 801, 821-5.

If there is a discrepancy between this tendency and the willingness of international tribunalsto allow special custom to override general custom, it can be explained by recalling that lexspecialis derogat generali is a maxim of interpretation, i.e, a means of giving effect to the presumedintention of the law-giver. Thus it applies to treaties and custom, because the creation of treatiesand (to some extent) of custom is an intentional activity, but not to general principles of law,which are not intentionally created as a source of international law but are simply the by-productof similarities between municipal laws (it is hardly to be supposed that a State would enact a rulein its own law with the intention of fostering the growth of a general principle of law which wouldbe advantageous to that State on the international plane).

I Fedozzi's argument in the Lotus case, reprinted in Marek, Repertoire des decisions et desdocuments . . . de la P.C.I.J. et de la C.I.J., series I, vol. 2 (1967), p. 874; Right of Passage case,I.C.J. Reports, 1960, pp. 6, 90, per judge Moreno Quintana dissenting.

2 UnitedNations Conference on International Organization (I945), vol. 13, p. 164; British argu­ment in the CorfuChannel case, I.C.J. Reports, 1949,PP. 4, 99; UnitedNationsConference ontheLawoj Treaties, Official Records, First Session, p. 198, para. 5; ibid., Second Session, p. 67, para. 9.

3 Castaiieda, Legal Effects of United Nations Resolutions (1969), p. 227.4 See below, pp. 275 and 279. 5 Recueil des cours, 54 (1935), pp. S, 212.6 Some explanations for this state of affairs are suggested in Akehurst, A ModernIntroduction

to International Law, second edition (1971), p. 58.7 Acquisition of Polish Nationality (1923), P.C.I.J., Series B, NO.7, p, 16; Treatmentof Polish

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prevail over custom; the treaties in the cases in question were probably simply morespecific, or later in time, than the conflicting customary rules.

It is sometimes said that treaties prevail over custom by virtue of the maxim lexspecialis derogat generali.' It often happens that the subject-matter of a treaty is morespecific than a customary rule, or that the States bound by a treaty are fewer than theStates bound by a customary rule. But it is equally possible that a customary rule maybe more specific than a treaty, or that a special custom binding a small number ofStates may conflict with a multilateral treaty binding a large number of States; insuch cases the maxim lex specialis derogat generali causes the customary rule toprevail over the treaty.>

Where the maxim lex specialis derogat generali provides no clear guidance, or whereit is shown not to reflect the intentions of the States concerned, it seems that treatiesand custom are of equal authority.' The later in time prevails..~ A treaty can overridepre-existing custom, but subsequent custom can override a treaty. This view comesnaturally to writers who regard custom as an implied agreement between States,' butit is also shared by many writers of other schools." Termination of a treaty as a resultof the subsequent growth of a conflicting custom is an example of desuetude, a well­recognized method by which treaties can come to an end.?

However, just as there is a presumption against the establishment of new customaryrules which conflictwith pre-existing customary rules," so there is a presumption againstthe replacement of customary rules by treaties and vice versa. There is a presumptionof interpretation (rebuttable, like all presumptions of interpretation) that treaties arenot intended to derogate from customary law, just as statutes in English law are

Nationals (1932), P.C.I.J., Series AlB, No. 44, pp. 23-4; Lighthouses case (1934), ibid., No. 62,p. 25; Eastern Greenland case (1933), ibid., No. 53, p. 76, per Judge Anzilotti dissenting. See alsothe North Sea Continental Shelf cases, I.C.J. Reports, 1969, pp. 3, 24.

I P.C.!.J., Advisory Committee of Jurists, Proces-Verbaux of the Proceedings of the Committee,1920, p. 337 (Ricci-Busati). And see above, p. 274 n. 3.

2 Le Fur, Recueil des cours, 54 (1935), pp. 5, 209.3 Despite occasional statements that treaties have a higher hierarchical authority than custom;

see above, p. 274 n. 1 (but cf. n. 2) .

• With the possible exception of cases where it can be proved that the parties intended other­wise; cf. Article 30 (2) of the Vienna Convention on the Law of Treaties.

5 According to such writers, the only difference between treaty and custom is one of form;a treaty is an express agreement and custom is an implied agreement. Since treaty and customare two different forms of the same thing, they are equal to one another in authority; a subsequenttreaty overrides an earlier custom, and a subsequent custom overrides an earlier treaty, just asa subsequent treaty overrides an earlier treaty. See Strupp, Recueil des cours, 47 (1930), p. 330;Tunkin, Theory of International Law (1974), p. 142.

6 Heilborn, Recueil des cours, II (1926), pp. 5, 29; Castberg, ibid., 47 (1933), pp, 313, 338;Reuter, ibid., 103 (1961), pp. 426, 484; Monaco, ibid., 125 (1968), pp. 93, 213-14; Capotorti,ibid., 134 (1971), pp. 427, 516; Paul de Visscher, ibid., 136 (1972), pp. I, 79; Kosters, 'Lesfondements du droit des gens', Bibliotheca Visseriana, 4 (1925), p. 249; Sereni, Diritto inter­nasionale, vol. I (1956), p. 143; Verzijl, International Law in Historical Perspective, vol. I (1968),p. 85. See also the writers cited by Tunkin, op. cit. (previous note), p, 142.

7 McNair, The Law of Treaties (1961), pp. 508, 516-18; Pinto, Recueil des cours, 87 (1955),pp. 391,431-3; International Law Commission's 1966 report, American Journal of InternationalLaw, 61 (1967), p. 388 (identifying desuetude with implied consent). The addition at the ViennaConference of the words 'after consultation with the other contracting States' to what is nowArticle 54 (b) of the Vienna Convention on the Law of Treaties was apparently not intendedto prevent the operation of desuetude: United Nations Conference on the Law of Treaties, OfficialRecords, First Session, p. 476.

8 See the author's article on custom, above, p. 1 at p. 19.

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presumed not to derogate from the common law. Similarly, subsequent custom canterminate a treaty only when there is clear evidence that that is what the parties intend.In particular, if the treaty provides for denunciation and if the parties believe that anew customary rule conflicts with the treaty, one would expect them to denounce thetreaty; failure to denounce strengthens the presumption that the treaty has not beenreplaced by a subsequent conflicting customary rule.'

The clearest evidence that the treaty has been replaced by a subsequent conflictingcustomary rule is to be found in statements (unilateral or otherwise) by the partiesrecognizing that this has occurred. If all the parties to the treaty make such statements,that is conclusive; but statements by only some of the parties are strongly persuasive(especially if a high proportion of the parties make such statements), provided that theother parties do not object. Z

The Committee of Jurists investigating the Aaland Islands dispute said that viola­tion by a party of its obligations under a treaty, coupled with acquiescence by theother parties, could not terminate the treaty.s Although this view seems excessivelystrict, there is a need for evidence that the parties believed that the treaty had ter­minated- or intended that their acts should terminate it. In the absence of expressstatements concerning termination, such evidence can only be provided by abundantand consistent practice. It is sometimes suggested that the widespread violations ofsome of the laws of war during both world wars have given rise to new customaryrules which have terminated the relevant treaties, but it is doubtful whether the practicewas sufficiently consistent to have that effect.!

Where the treaty permits but does not require a State to act in a particular way, itis dangerous to infer desuetude from failure to act in that way.6

In all cases, what counts is the practice followed inter seby the parties to the treaty;the practice which they follow in their dealings with States which are not parties to thetreaty, and the practice of the latter States, may give rise to a rule of customary law,but such a rule has no effect on the treaty unless it is followed by the parties to thetreaty in their relations with one another."

just as a new customary rule can terminate a treaty, it can also amend a treaty.s

1 Cf. North Sea Continental Shelf cases, I.C.J. Reports, 1969, pp. 3, 25: '... when a numberof States ... have drawn up a convention specifically providing for a particular method by whichthe intention to become bound by ... the Convention is to be manifested ..., it is not lightly to bepresumed that a State which has not carried out these formalities, though at all times fully ableand entitled to do so, has nevertheless somehow become bound in another way.'

:z Cf. the Reichsgericht's decision in S.E. v, G. and Gen. (1925) (English translation in Briggs,The Law of Nations, second edition (1952), p. 902).

3 League of Nations, Official Journal, Special Supplement NO.3 (1920), p. 16... Yuille, Shortridge case (1861), de La Pradelle and Politis, Recueil desarbitragesinternationaux,

vol. 2, second edition (1957), pp, 78, 108.S For instance, some of the violations provoked protests, and there has been a partial revival of

respect for the old treaties since 1945: Akehurst, A Modern Introduction to International Law,second edition (1971), pp. 329-30. Moreover some of the violations during both world wars werejustified as reprisals, which clearly negates the existence of a belief on the part of the belligerentsthat the treaties were no longer in force. See also below, p. 277, at n. 6.

6 Schwarzenberger, International Law, vol. I, third edition (1957), pp. 536-7.7 See also Thirlway, International Customary Law and Codification (1972), p. 132.8 A special (e.g, regional) custom followed by only some of the parties to the treaty can amend

the Treaty as between those parties, although it does not affect their relations with the otherparties: Thirlway, International Customary Law and Codification (1972), p. 139. Such a customcan presumably suspend the operation of the treaty as between the States bound by the custom(cf. Article 58 of the Vienna Convention on the Law of Treaties).

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This is what happened in the Air Transport Services Agreement Arbitration of

1963.1

Article 38 of the International Law Commission's 1966 Draft Articles on the Lawof Treaties provided:

A treaty may be modified by subsequent practice in the application of the treatyestablishing the agreement of the parties to modify its provisions.

This provision was deleted at the Vienna Conference by 53 votes to 15, with 26absten­tions.> However, only 10 of the 26 States which spoke in favour of the proposal todelete said that Article 38 was not in accordance with existing law; 3 States supporteddeletion because they thought that it was inappropriate for the Convention to deal withrelations between treaties and customary law; I I States said that the rule laid down inArticle 38 was undesirable, but did not say whether or not it was in accordance withexisting law; the remaining 2 of the 26 States advocated deletion without givingreasons. It is thus difficult to interpret the deletion of Article 38 as a clear rejection ofthe view that existing law allowed a treaty to be amended by subsequent practice,especially since the Vienna Convention did not exclude the possibility of terminationof treaties by desuetude.! and expressly allowed a treaty to be interpreted in the lightof subsequent practice (Article 3 (3) (b)); amendment merges into termination at oneextreme and into interpretation at the other extreme. Of course, even if the deletion ofArticle 38 represented, as it probably did, progressive (or retrogressive) developmentrather than codification, it is possible that customary law will in the future reject theidea that a treaty can be amended by subsequent practice; but it is equally possiblethat customary law will not reject that idea, and that even the Vienna Convention onthe Law of Treaties will be amended by subsequent practice.

The opposition to Article 38 at the Vienna Conference was largely inspired bycriticism of the Air Transport Services Agreement Arbitration,4 and by resulting fearsthat treaties which had been ratified by a State's legislature could be modified by the actsof low-ranking officials. These fears are not entirely unfounded (customary rules canbe created by the practice of low-ranking officials), but they are somewhat exaggerated.-the presumption against changing legal rules! means that treaties can be amendedonly by prolonged practice, and the need for prolonged practice gives higher authoritiesin the State concerned the opportunity to discover and stop the activities of low-rankingofficials before it is too late. Moreover, as Tunkin rightly observes:

... only such practice as shows an agreement of the parties may introduce a change in atreaty ... Individual digressions from treaty provisions, ... [which] have taken placewith the common consent of the parties, but [which] do not testify to their intention tochange a treaty provision, do not modify the treaty."

Subsequent practice often modifies the constituent treaties of international organiza­tions.? Some authorities maintain that such modifications need the consent of all

I I.L.R. 38, pp. 182,249 et seq. See also the Preak Vihear Temple case, I.C.J. Reports, 1962,pp. 6, 21 et seq.; Fitzmaurice, this Year Book, 33 (1957), pp. 203, 212, 225, 252; Reuter,Introduction au droit des traites (1972), p. 135.

2 United Nations Conference on the Law of Treaties, Official Records, First Session, pp. 207-15.3 See above, p. 275 n. 7. 4 See above, n. I. 5 See above, pp. 275-6.6 Tunkin, Theory of International Law (1974), p. 146. Practice cannot create customary law

unless it is accompanied by opinio juris.7 For pre-war examples, see Kopelmanas, this Year Book, 18 (1937), pp. 127, 139-40. Tunkin,

op. cit. (previous note), p. 339, argues that basic provisions of the constituent treaty cannot beamended by practice. This distinction seems illogical (cf. above, p. 275 n. 5). Even if the basic

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member States of the organization;1 others argue that a majority is sufficient."The truesolution would appear to be to apply by analogy any amendment clause which existsin the constituent treaty; thus, the United Nations Charter can be amended by a prac­tice supported by two-thirds of the member States, including the five permanentmembers of the Security Council.! If the treaty does not provide for amendment bya majority of the members, subsequent practice can amend the treaty erga omnes onlyif it is unanimous, or, to be more precise, unopposed.!

On the other hand, even practice which is opposed by some members can interpretthe treaty, especially if the treaty empowers the organization to take decisions bymajority vote; the persuasiveness of the interpretative practice varies according to theproportion of the members which support it. There is therefore a temptation for Statesto argue that practice which conflicts with the treaty is merely an interpretation of it.At all events, the distinction between amendment and interpretation is often blurred inpractice.! For instance, the practice of the Security Council, whereby an abstentionby a permanent member is not treated as a veto, is described by some authorities as anamendment of the Charters and by others as an interpretation."

General principles of law

The expression 'general principles of law' can refer to one of two different things­general principles of international law, and general principles borrowed from muni­cipal Iaw.f

General principles of international law are not a separate source of internationallaw. They are simply broad principles, such as the principle of diplomatic immunityor the principle of the freedom of the seas; most of them are principles of customarylaw, although there is no logical reason why they should not be derived from othersources, such as treaties. Some of them are so well-known that lawyers and judges findit unnecessary to cite authority to support thern.? Others are more controversial; forprovisions are jus cogens (which is unlikely to be the case), the tacit consent of the vast majorityof the members of a universal organization is probably enough to change jus cogens; cf. Tunkin,op, cit., p. 160, and see below, p. 285.

J Tunkin, op, cit. (above, p. 277 n. 6), p. 339; Expensescase, I.e.J. Reports, 1962, pp. 151, 191,per Judge Spender. Presumably such authorities would not deny that the practice of a majority(or even a minority) of member States can amend the treaty inter se; see above, p, 276 n. 8.

a Rajan, United Nations and DomesticJurisdiction, second edition (1961), p. 405.3 On the other hand, the requirement of ratification laid down in Article 108 of the Charter is

a purely procedural formality, which can be waived by the States concerned (pace Judge Spenderin the Expenses case, I.C.J. Reports, 1962, pp. 151, 191).

4 See the author's article on custom, above, p. I at pp. 23-4. Cf. Judges Winiarski and Busta­mante in the Expenses case, I.e.J. Reports, 1962, pp. 151,230-3,300, although they overlook theimplications of Article 108. 5 Jessup, A Modern Law of Nations (1948), p. 16.

6 Tunkin, Theory of International Laic (1974), pp. 339-40; Greig, International Law (1970),pp. 382-3; Sperduti, Rivista di diritto internazionale, 44 (1961), pp. 3, 12; Fitzmaurice, thisYear Book, 30 (1953), pp. I, 55; Gross, American Journal of International Law, 62 (1968), pp.315, 328; Judge Bustamante in the Expenses case, I.e.J. Reports, 1962, pp. 151,291; Judgede Castro in the Namibia case, ibid., 1971, pp. 16, 185-6.

7 Namibia case, I.C.J. Reports, 1971, pp. 16, 22, 117, 153-4.8 Some principles are general principles of law in both senses, but not all of them are. The

attempt by Cheng, General Principles of Law (1953), to blur the distinction between the twomeanings of general principles of law is unsound; see E. Lauterpacht's review of Cheng's bookin this Year Book, 30 (1953), p. 544. See also Akehurst, The Law Governing Employment in Inter­national Organizations (1967), pp. 77-8, and A Modern Introduction to International Law, secondedition (1971), pp. 51-2.

9 Serensen, Manual of Public International Law (1968), p. 144.

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instance, a lawyer may try to infer from several specific rules of customary law anunderlying principle which has not been perceived by anybody else before. 1

The hierarchical position of general principles of international law depends on thesource from which they are derived. However, owing to their generality, they are oftenousted by rules of a more specific character (including rules derived from hierarchicallylower sources), in application of the maxim lex specialis derogat generali.

General principles of law, in the sense of principles borrowed by international lawfrom municipal law, were mentioned in Article 38 of the International Court's Statutein order to enable the Court to fill gaps in treaties and customary law; they can there­fore be applied only in the absence of rules (or at least specific rules) of treaty law orcustomary Iaw.> Case law! and, with a few exceptions, writers- are unanimous in hold­ing that treaties and custom override general principles of law in the event of conflict.

However, it is permissible to use general principles of (municipal) law to interprettreaties and custorn.! Moreover, general principles of law are sometimes more specificthan very broad principles laid down by treaties or customary law, and in such casesthe maxim lexspecialis derogat generali can sometimes lead to general principles of lawbeing applied in preference to very broad principles laid down by treaties or customarylaw. For instance, the presumption in favour of the liberty of State action, which,according to the Lotuscase, is a principle of customary law, would suggest that a Stateis under no duty to pay moratory interest on its debts; and yet the Permanent Courtof Arbitration held in the Russian Indemnity case that such a duty existed, based ona general principle of (municipal) law."

Judicial decisions and the writings of publicists

Judicial decisions and the writings of publicists are described in Article 38 of theInternational Court's Statute 'as subsidiary means for the determination of rules of

I Much the same sort of thing happens when existing rules are extended by analogy. Anargument by analogy is in effect an argument that specific rules reflect a broader (and oftenunstated) principle which is applicable not only to the circumstances governed by the specificrules but also to analogous circumstances. On analogy generally, see Giuliano, Rivista di dirittointernazionale, 20 (1941), p. 69.

In view of the reluctance by Soviet international lawyers to admit that international judges areentitled to extend rules by analogy, it is interesting to note that Soviet law instructs judges tofill gaps in the codes by resort to analogy: David and Brierley, Major Legal Systems in the WorldToday (1968), p. 179. However, such use of analogy is now forbidden in criminal cases, althoughit used to be practised in Stalin's time, when, for instance, a provision of the criminal code for­bidding hunting without a permit was applied by analogy to a man who ran off with anotherman's wife.

Z P.C.I.J., Advisory Committee of Jurists, Proces-Verbaux of the Proceedings of the Committee,1920, p. 338.

3 Russian Indemnity case (1912), R.I.A.A., vol. II, pp. 431, 441; Chorz6w Factory case (1927),P.C.I.J., Series A, No. 13, p. 27, per Judge Anzilotti dissenting; Fisheries case, I.C.J. Reports,1951, pp. 116, 147-8,per Judge Alvarez; Right of Passagecase, I.e.J. Reports, 1960, pp. 6,43-4;Castillo v. Zalles (1955), I.L.R. 22, p. 540 (Supreme Court of Chile).

4 Le Fur, Recueil des cours, 54 (1935), pp. 5, 213 i Habicht, ibid., 49 (1934), pp. 297-8; Rous­seau, Droit international public, vol. 1 (1970), p. 395; Hsiung, Law and Policy in China's ForeignRelations (1972), p. 22; Avramov, Jugoslovenska revija sa medunarodnopravo, 3 (1959), p. 385.Contra, Degan, L'equite et le droit international (1970), p. 17 (who regards general principles oflaw as possessing the same value as treaties and custom), and the authors mentioned below,p. 282 n. 5.

5 Le Fur and Habicht, loco cit. (previous note). For a bold example of this technique, see theMosul case (1925), P.C.I.J., Series B, No. 12, p. 32.

6 R.I.A.A., vol. I I, p. 431 (see also the dictum on p. 443 about force majeure).

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law'. This suggests that they have a lower hierarchical value than treaties, custom andgeneral principles of law.' Indeed, some writers do not regard them as sources at all,but only as indirect and secondary evidence of rules created by the true sources­treaties, custom and general principles of Iaw.'

It is sometimes said that decisions of international courts carry greater weight thandecisions of national courts, which in turn carry greater weight than the writings ofpublicists.! This is true more often than not, but there can be exceptions; it would beinvidious to name names, but all of us can think of certain writers who have enjoyeda greater reputation than certain judgments of national courts, or of certain judgmentsof national courts which have enjoyed a greater reputation than certain judgments ofinternational courts. Much depends on the quality of the reasoning which the judge orwriter employs.! The absence of any rule of binding precedent in international lawmeans that judgments do not always carry greater weight than the writings of publicists.

Otherpossible sources of law

Having discussed the sources (or pseudo-sources) of international law listed inArticle 38 (1)of the International Court's Statute, it remains for us to examine variousother things which are sometimes said to be sources of international law.!

The position of equity in the hierarchy of the sources of international law is extremelylow. It is universally agreed that an international tribunal cannot apply equity in amanner which conflicts with international law unless it has been specifically authorizedto do so. In the absence of such an authorization, the most that an international tribunalcan do is to use equity to fill gaps in the law and to make equitable exceptions to legalrules. When equitable exceptions are made to legal rules, it sometimes appears as ifequity is overriding the law, but this appearance is misleading. All that the judge isdoing is holding that the legal rule does not apply to the facts of the case; he is dis­tinguishing it, just as a first-instance judge in England can distinguish a House ofLords decision. The English judge does not deny that the House of Lords decision isbinding on him; he merely holds that it does not apply to the facts of the case. Aninternational judge does the same; he does not deny that the legal rule is binding, hemerely holds that it does not apply to the facts of the case. The equitable exception isapplicable and the legal rule is not, because the equitable exception is more specificthan the legal rule; lex specialis derogat generalis

Unilateral acts of States are sometimes described as a source of international lawby lawyers from civil law countries in Western Europe." However, these acts are so

I This is supported by what little authority there is on the topic: Marek, op, cit. (above, p. 274n. I), pp. 51, 874; British argument in the Corfu Channel case, I.C.]. Reports, 1949, pp. 4, 99;South West Africa cases, ibid., 1962, pp. 319, 576, per Judge ad hocvan Wyk dissenting; BarcelonaTraction case, I.C.]. Reports, 1970, pp. 3" 315-16 (separate opinion of Judge Ammoun).

2 e.g, Schwarzenberger, International Law, third edition, vol. I (1957), pp. 26-8.3 Schwarzenberger, op. cit. (previous note), pp. 3°-7; Fitzmaurice in Symbolae Verzijl (1958),

p.172... Schwarzenberger, Current Legal Problems, 9 (1956), pp. 235, 238.5 Natural law is discussed below, pp. 282-3.6 The way in which an international judge distinguishes customary rules is very similar to the

way in which an English judge distinguishes judicial decisions. In the case of treaty provisions,the process of distinguishing takes a slightly different form; the judge bases his decision on thepresumed intention of the parties, arguing that the parties cannot have intended the letter of thetreaty to apply in cases where it would produce injustice.

7 Rousseau, Droit international public, vol. I (1970), pp. 416-32, and the authors citedby him.

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heterogeneous that it is very difficult to generalize about them. I Very often they arenot sources of law. For instance, in many circumstances, protests, waiver and ac­quiescence are merely steps towards the formation of a customary rule or a prescriptiveright, and are therefore not sources of law, or even of legal rights and obligations, intheir own right. Similarly, notification (or lack of it) has legal effects only if there isa rule of international law, derived from some other source, which requires notificationand attributes legal effects to it; consequently notification is not a source of law, oreven of legal rights and obligations, in its own right. However, in other circumstancesunilateral acts are sources of law, or at least of legal rights and obligations: a State cansometimes assume obligations by promise or lose rights by waiver (such a promise orwaiver may occasionally be inherent in recognition). Such acts are similar in theireffects to treaties, and probably have the same hierarchical value as treaties; that is tosay, a State can, by promise or waiver, lose liberties or rights which it enjoyed undertreaties or customary rules, although a subsequent treaty or custom can extinguish theobligations assumed in the promise or revive the rights lost by the waiver.

Many acts of international organizations are not sources of international law in theirown right, either because they are merely part of the practice from which customaryinternational law develops," or because they merely record agreements between (orpromises by) States.' However, every international organization has an inherent powerto take binding decisions on questions which fall within the internal law of the organiza­tion: and a power to take binding decisions on other questions may be conferred by theconstituent treaty.! It would require a separate article to examine the place of suchbinding decisions in the hierarchy of the sources of international law, because theproblems which arise are inseparable from a whole host of questions which form part ofthe law of international organizations but which would be out of place in a generalarticle on the sources of international law-the principles governing interpretation ofconstituent treaties of international organizations, the doctrine of implied powers, thequestions whether an organ of an international organization can delegate its powersand whether it is bound by its own rules of procedure, the question whether theinternal law of an international organization is a separate system of law from inter­national law, the question whether the European Communities are different in naturefrom other international organizations, the difference between void and voidable acts.The omission of discussion of binding decisions of international organizations from thepresent article is not as serious as it may seem, because (with the exception of theEuropean Communities and the internal law of international organizations, both ofwhich are specialized topics) international organizations seldom take binding decisions.

Jus cogens

Everything said hitherto in this article must be regarded as subject to the rules ofinternational law concerning jus cogens. In the event of a conflict between a rule of juscogens and a rule of jusdispositivum, the rule of juscogens must prevail, regardless of thesources of the conflicting rules, regardless of whether the rule of jus dispositioum came

I Verzijl, International Law in Historical Perspective, vol. 6 (1973), pp. 105-6. The list of suchacts given by Rousseau (op. cit., previous note) is as follows: notification, promise, recognition,protest, waiver, acquiescence.

2 See the author's article on custom, above, p. I at pp. 5-8 and II. Resolutions voted forby member States can interpret or even amend the constituent treaty of the organization; this isalso a form of customary law. See above, pp. 277-8.

3 Castaneda, Legal Effects of United Nations Resolutions (1969), chapter 6.• Or by another treaty: Castaneda, op. cit. (previous note), chapter S.

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into existence before or after the rule of jus cogens, and regardless of whether the ruleof jus dispositivum is more specific or less specific than the rule of jus cogem.

As regards the sources of international law which can produce rules of jus cogens,1a wide variety of views has been expressed by writers.' Some say that such rules arederived from custom,' while others say that they can be derived either from custom orfrom treaties.' A few maintain that they are derived from general principles of law,sor from either custom or general principles of law,6 or from either custom, treaties orgeneral principles of law.7 Judicial dicta speak of rules of juscogens being derived fromtreaties! or general principles of law,9 but without apparently implying that they arelimited to those sources. Some authorities have argued that treaties or customs whichconflict with basic principles of natural law are void;IO others reject this view."

The travaux preparatoires of the Vienna Convention on the Law of Treaties reveala more consistent picture. The reports of the International Law Commission said that

1 No one has ever suggested that all the rules derived from a particular source are jus cogent,References to a source's being capable of producing rules of jus cogens merely mean that some ofthe rules derived from that source are or may be rules of jus cogens.

2 In addition to the writers listed below, see also the writers whose views are summarized inSztucki, Jus Cogens and the Vienna Convention on the Law of Treaties (1974), pp. 74-6, andCarnegie Endowment for International Peace, The Concept of Jus Cogens in International Law(1967), pp. 12 and 26-49.

3 Brownlie, Principles of Public International Law, second edition (1973), p. 5°°; Reuter,Introduction au droit des traius (1972), pp. 139-40.

4 Verzijl, International Law in Historical Perspective, vol. I (1968), p. 85; Hsiung, Law andPolicy in China's Foreign Relations (1972), p. 29; Le Fur, Recueil des cours, 54 (1935), p. 43;Verdross, American Journal of International Law, 60 (1966), pp. 55, 61; Morelli, Rivista di dirittointernazionale, 51 (1968), pp. 108, 110; Aleksidze, Soviet Year Book of International Law (1969),pp. 127, 149; Tunkin, Theory of International Law (1974), p. 158, citing McNair.

5 Von der Heydte, Die Friedensuiarte, 33 (1933), pp. 289, 290, 297-8; Harle, Revue de droitinternational et de Ugislation comparee,third series, 16 (1935), pp. 663, 680-1; Verdross, Annuairede l'Institut de droit international (1937:), pp. 186-9. These authors considered that generalprinciples of law were normally subsidiary to treaties and custom; only a few general principlesof law were jus cogens, overriding treaties and custom. Such views represented only a passingphase in the thinking of Verdross; cf. his earlier views in Annuaire de l'Institut de droit inter­national (1932), pp. 292-3, and his later views in the article mentioned in the previous note.

6 Mann, in Festschrift fur Ulrich Scheuner (1973), pp. 399, 401.7 P. de Visscher, Recueil des cours, 136 (1972), pp. I, 107.8 Koch case (1959), I.L.R. 30, pp. 496, 503.9 Right of Passage case, I.C.J. Reports, 1960, pp. 6, 135, 139-40, per Judge ad hoc Fernandes

dissenting; South West Africa cases, ibid., 1966, pp. 6, 298, per Judge Tanaka dissenting.10 Vattel, The Law of Nations, introduction, paragraphs 9 and 26, and Book II, paragraph 161;

Kosters, 'Les fondements du droit des gens', Bibliotheca Visseriana, 4 (1925), pp. 183-7; Kunz,American Journal of International Law, 47 (1953), pp. 662, 666; North Sea Continental Shelfcases, I.C.J. Reports, 1969, pp. 3, 193, per Judge Tanaka dissenting. See also the writers citedby Sztucki, op. cit. (above, n. 2), pp. 59, 66, 110.

Many writers say that immoral treaties are void. However, although natural law can possiblybe regarded as a formal source of international law, morality clearly cannot. The writers whoargue that immoral treaties are void do not generally say what the formal source of this rule is.It might be natural law; alternatively, it might be customary law or some other 'positivist' source.

11 See the writers listed in Sztucki, op, cit. (above, n. 2), pp. 60-6. See also The Antelope(1825), 23 U.S. 66, 120-2 and The Enterprise (1855), Moore, International Arbitrations, vol. 4(1898), pp. 4349, 43 60- r , 4373, 4377· In addition, many writers, especially before 1960, deniedthe existence of any form of jus cogens, and therefore opposed the view that treaties and customconflicting with natural law were void: Sztucki, op. cit., pp. 55-8, and Kosters, lococit. (previousnote), pp. 187-9. Authorities basing jus cogens solely on treaties, custom and/or general principlesof law must also be regarded as rejecting the view that natural law can be a formal source ofjus eogens.

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jus cogens could be established by treaty or by custom. r At the Vienna Conference,some States said that jus cogens could be derived from custom," or treaties,s or both.sThe view that treaties are one of the possible sources of juscogens also receives supportfrom speeches by several delegates who listed rules contained in the United NationsCharter or in other treaties as examples of jus cogens, without stating that those ruleswere also rules of customary law.S

There was little support at the Conference for the view that jus cogens could bederived from rules other than treaties and custom. In particular, a United Statesamendment, defining a rule of jus cogens as a rule 'which is recognized in common bythe national and regional legal systems of the world and from which no derogation ispermitted', which might have been interpreted as defining jus cogens by reference togeneral principles of law (although delegates differed as to the true meaning of theamendment), was defeated by 57 votes to 24, with 7 abstentions.

Some delegates at the conference said that the provisions of the Convention con­cerningjus cogens gave effect to principles of international morality." That may be true,but the important thing to note is that the Convention defined a rule of jus cogens, notby reference to subjective notions like morality, but as a 'norm accepted andrecognizedbytheinternational community of States asa whole as a norm from which no derogationis permitted'.' Moreover, the consensus at the conference was apparently that rules ofjus cogens could be derived only from treaties and/or custom; in other words, principlesof international morality had to take the form of conventional or customary rules ofinternational law in order to have any chance of becoming jus cogens.8

Moreover, there are arguments of principle which support the view that jus cogenscan be derived from treaties and custom, but not from other sources of internationallaw. We have already seen that treaties and custom are normally of equal authority assources of international law, and override other sources. It would be an anomalousdeparture from that general pattern if rules of jus cogens could be derived from custombut not from treaties (or vice versa), or if other sources, which are normally inferior totreaties and custom, could produce rules of juscogens which would override treaties andcustom. Furthermore, the Vienna Convention says that a rule of jus cogens must be

I American Journal of International Law, 58 (1964), pp. 265-6 and 291; ibid., 6r (1967), p. 411('the jurisprudence of international tribunals', mentioned on p. 410, was probably intended toserve as evidence of existing rules of jus cogens, not to create new rules of jus cogens).

2 United Nations Conference on the Law of Treaties, Official Records, First Session, pp. 295(Greece), 311 (Italy, but see below, n. 5), 320 (Ivory Coast).

3 Ibid., p. 315 (Ethiopia); ibid., Second Session, p. 97 (Ecuador and Cuba). These States madeit clear that they did not regard treaties as the sole source of jus cogens,

4 Ibid., First Session, pp. 297 (Cuba), 298 (Chile), 302 (Poland), 326 (Malaysia), 327(Trinidad), 387 (Cyprus); ibid., Second Session, p. 99 (Poland).

5 Ibid., First Session, pp. 294 (U.S.S.R.), 296 (Kenya), 297 (Cuba and Lebanon), 298 (Nigeria),300 (Sierra Leone), 301 (Madagascar), 302 (Poland), 307 (Byelorussia), 311 (Italy), 317 (Australia),318 (Czechoslovakia), 320 (Ecuador), 324 (Switzerland); ibid., Second Session, pp. 96-7 (Ecua­dor) and 100 (Ukraine).

6 Capotorti, Recueil des cours, 134 (197r), pp. 417, 522.7 Italics added. These words have distinctly positivist or consensual overtones.8 A few members of the International Law Commission and a few delegates at the conference

said that jus cogens was based on natural law; a few others attacked this view (Sztucki, op, cit.(above, p. 282 n. 2), pp. 60-3). The view ofthe majority seems to have been that jus cogens couldbe derived only from treaties and/or custom, thus impliedly rejecting the view that natural lawcould be a formal source of jus cogent independently of treaties and custom. Rules of natural lawwould therefore have to be incorporated in treaties or custom before they stood any chance ofbecoming jus cogens,

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'accepted and recognized by the community of States asa whole'I-an expression which,as we shall see in a moment, is not free from difficulty, but which surely suggests thata rule of jus cogens cannot come into being unless it is accepted and recognized by atleast a very large number of States, including the two super-powers. But the SovietUnion refuses to recognize any sources of international law other than treaties andcustom. This negative attitude, coupled with the definition of jus cogens given in theVienna Convention, presents an almost insuperable obstacle to the development ofjus COgens out of any source other than treaties and custom. Finally, as far as generalprinciples of (municipal) law are concerned, not all principles of municipal law aresuitable for transposition to the international environment, and the factors which makea broad definition of jus cogens workable in municipal law hardly exist in internationallaw;2 it is therefore a great mistake to argue that the fact that a particular rule is juscogens in all municipal legal systems means that it is jus COgens in international law also.

One of the requirements which must be met, according to the Vienna Convention,before a rule can be regarded as a rule of jus cogens, is that it must be a rule of 'generalinternational law'. Some writers identify general international law with customarylaw.t However, this is doubtful. A treaty which has been ratified by all or almost allthe States in the world is as much a part of general international law as most customaryrules. Similarly the use of the word 'emerges' in Article 64 of the Vienna Conventionseems at first sight more apt to describe the gradual development of a customary rulethan the conclusion of a treaty. But it does not necessarily rule out treaties, because itmay take a long time for a treaty to receive a sufficiently large number of ratificationsfor the treaty to be regarded as jus cogens. Besides, the French text uses the word'survient', and, as the French delegate at the Vienna Conference said, 'the dictionarydefinition of the French verb "survenir" implied something sudden and unexpected'.4

A more serious difficulty arises from the requirement, laid down in Article 53 of theVienna Convention, that a rule of jus cogens must be 'accepted and recognized by theinternational community of States as a whole'. Some delegates at the Vienna conferencethought that rules of jus cogens must be accepted by all States s others thought thatthey must be accepted by an overwhelming majority of States, but not by all." Eachinterpretation gives rise to problems.

The 'unanimity' interpretation would make the development of jus cogens difficult­and would make the development of jus cogens by treaty extremely difficult, because itis most unlikely that all the States in the world would be parties to a treaty. However,it is not a logical impossibility that all the States in the world might become partiesto a treaty. 7

I Italics added.2 Marek, in Melanges Guggenheim (1967), pp. 426, 429 et seq.: Rousseau, Droit international

public, vol. I (1970), p. IS0; Sinclair, The Vienna Convention on the Law of Treaties (1973),pp. 114-15.

3 e.g, Thirlway, International Customary Law and Codification (1972), p. 97.4 United Nations Conference on the Law of Treaties, Official Records, Second Session, p, 124,

para. 17. The Spanish text uses the words 'aparici6n' and 'sorge',5 Ibid., First Session, p. 294, para. 12 (Finland), p. 295, para. 17 (U.S.A.) and para. 19 (Greece),

p. 311, para. 40 (Israel), p, 323, para. 16 (Philippines); ibid., Second Session, p. 96, para. 29(West Germany).

6 Ibid., First Session, p. 301, para. 19 (Ghana), p. 312, para. 52 (New Zealand), p. 317, para. 17(Australia), p. 318, para. 2S (Czechoslovakia); ibid., Second Session, p. 106, para. 63 (Libya).See also the statement by the Chairman of the Drafting Committee, ibid., First Session, p. 471,para. 7, and p. 472, para. 12.

7 See also below, p. 285 n. 4.

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The 'overwhelming majority' interpretation causes more difficulties. The normalrule is that a State is not bound by a treaty to which it is not a party. In certain circum­stances a dissenting State is not bound by rules of customary law; indeed, the travauxpreparatoires of Article 38 of the Vienna Convention suggest that a State is not boundby a new customary rule unless it has positively consented to that rule. I What happensto the States which oppose the creation of a rule of jus cogens? Some authorities arguethat they are not bound by it. 2 This is logical, but undesirable; jus cogens would losemuch of its raison d'etre if States could escape its binding force by dissenting from it.Other authorities argue, rather illogically, that dissenting States are bound by customaryrules of jus cogens but not by customary rules of jus disposiiioumi: however, apparentlynobody has yet argued that treaties laying down rules of jus cogens are binding on Stateswhich are not parties to them.

The true solution is probably that the dispute between the 'unanimity' interpretationand the 'overwhelming majority' interpretation is more apparent than real. There aretwo questions involved-how many States must recognize a rule as law, and how manymust recognize it as jus cogens? Most of the delegates who spoke in favour of the'unanimity' interpretation were addressing their minds to the first question, and mostof the delegates who spoke in favour of the 'overwhelming majority' interpretationwere addressing their minds to the second question. The true answer appears to be thata rule, in order to qualify as jus cogens, must pass two tests-it must be accepted aslaw by all the States in the world.s and an overwhelming majority of States must regardit as jus cogens»

I See the author's article on custom, above, p. I at pp. 23-7, especially p. 24 n. I.

2 Tunkin, Theory of International Law (1974), pp. 158-9. Cf. Lukashuk, in Carnegie Endow­ment Conference on the Process of Change in International Law, ed. Zacklin (1965), pp. 20-1, whosays that a State can choose between accepting rules of jus cogens and not being regarded as amember of the international community.

3 United Nations Conference on the Law of Treaties, Official Records, First Session, p. 197,para. 73, and p. 444, para. 49 (Venezuela); Aleksidze, Soviet Year Book of International Law(1969), pp. 127, 149; Thirlway, International Customary Law and Codification (1972), p. 110;Bokor-Szego, New States and International Law (1970), chapter 2.

4 In the case of a treaty, this would mean that all the States in the world must be parties to thetreaty. In the case of a customary rule, positive consent by all States is not necessary, despite someunfortunate statements to the contrary at the Vienna Conference; it is sufficient that some Statesaccept the rule and that other States do not dissent from it (see above, pp. 23-'7). The unanimityrequirement would be met if some States were parties to a treaty laying down the rule and ifthe rule were binding on all other States qua customary rule.

S According to the principle of acte contraire, a rule of jus cogens will cease to bejus cogensif theoverwhelming majority of States decide that it is no longer jus cogens-even though it may stillremain a rule of law (d. Tunkin, Theory of International Law (1974), p. 160). The final relativeclause in Article 53 of the Vienna Convention on the Law of Treaties is badly drafted, because itimplies that a rule of jus cogens can be replaced only by a rule of jus cogens and not by a rule ofjus dispositioum.

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