1. De iure belli ac pacis, I, 1, XV, 1: “ius voluntarium divinum … ex voluntate divina ortum habet, quo discrimine a iure naturali, quod item divinum dici posse diximus, internoscitur”. The modest place reserved for the will of God allowed Grotius to make his system universally acceptable to non-Christians as well. Cf. II, 15, VIII (particularly with regard to treaties and other agreements).

2. The Province of Jurisprudence determined, 1832, Library of Ideas ed., pp. 129, 157.

3. Ago, R., “Positive Law and International Law”, 51 A.J.I.L. (1957) p. 693 ff.Google Scholar

4. “Was für mich nur gilt, weil ich es will, kann eben kein Recht zwischen mir und einem Anderen, mir Gleichen, erzeugen”, Fricker, , “Noch einmal das Problem des Völkerrechts”, 34 Zeitschrift für die gesamte Staatswissenschaft p. 368 ff, at p. 394Google Scholar, as quoted in Jellinek, G., Die rechtliche Natur der Staatenverträge, Vienna 1880, p. 46.Google Scholar

5. Jellinek, op cit., p. 45: “es ist das Völkerrecht kein überstaatliches Recht, sondern es entspringt formell derselben Quelle, wie alles objective Recht: dem Willen des rechtsetzenden Staates”. And at p. 7: “Somit hängt … die ganze juristische Existenz des Völkerrechts von dem Nachweise ab, dass der Staat durch seine Normen sich selbst verpflichten kann, dass es möglich ist, dass Verpflichtender und Verpflichteter in einer Person existiren können”. Jellinek deals with custom (op cit. p. 47) and reason (op. cit. p. 42) as sources of international law, but only incidentally. He has, however, a strong passage on the nullity of immoral treaties (op.cit. p. 59 ff).

6. “In principle, when a number of States … have drawn up a convention specifically providing for a particular method by which the intention to become bound by the regime of the convention is to be manifested –namely by the carrying out of certain prescribed formalities (ratification, accession), it is not lightly to be presumed that a State which has not carried out these formalities, though at all the times fully able and entitled to do so, has nevertheless somehow become bound in another way”. North Sea Continental Shelf Cases, I.C.J. Rep. 1969 p. 25.

7. “Elementary principles of morality” is the phrase used by the I.C.J. in its advisory opinion on “Reservations to the Genocide Convention”, I.C.J.Rep. 1951 p. 23Google Scholar. The authentic French text has “principes de morale”.

8. “L'effet créateur de droits et d'obligations ne saurait être attribué à la volonté, mais uniqucmcnt à l'ordre juridique positif (Rechtsordnung). Bien plus, ce n'est pas la volonté interne qui forme l'élément constitutif de l'acte juridique, mais la déclaration de volonté, ‘c'est-à-dire un fait tangible. social propre à faire supposer … l'existence d'une volonté’ [ Dereux, , De l'interprétation des actes juridiques privés, thèse Paris, 1905, p. 355 ]Google Scholar. La seconde moitié du XIXe siècle inaugure ainsi l'ére de l'Erklärungstheorie” (Rieg, A., “Le rôle de la volonté dans la formation de l'acte juridique d'après les doctrines allemandes du XIXe siècle”, Archives de philosophie du droit. Nouvelle serie. No. 3, 1957, p. 125 ff at p. 127.Google Scholar

9. In the Kantian sense of “das subjektive Prinzip des Wollens”. Grundlegung zur Metaphysik der Sitten, Akademie-Ausgabe, p. 400.Google Scholar

10. Within the limits of this paper we are unable to deal with such extensive problems as coercion or agency.

11. How to do things with words, 1962.

12. Thus, the contrast between the assumed identity of the Ottoman Empire and the Turkey that emerged from World War 1 and, on the other hand, the assumed non-identity of the Habsburg Monarchy and the Austria that emerged at the same time. Comprehensive analysis in Marek, K., Identity and Continuity of States in Public International Law, 2nd. ed., 1968.Google Scholar

13. Alternative classifications of “facts”, for the purpose of techniques of “fact-finding”, are to be found in an internal discussion-paper used by the Netherlands delegation to the 21st session of the General Assembly of the U.N. where the question of methods of fact-finding was on the agenda:

“A classification of types of facts –if it would be a classification that would correspond to any classifications of types of means to find the facts, and of types of ends for which the fact-finding takes place– might be attempted along two lines at least:

First classification

a) past facts

Examples: events that happened in the remote or recent past (Corfu Channel Case, Channel Islands Case, Red Cruisader Case); historic interpretation of texts (travaux préparatoires, ideas in the early twenties on the “sacred trust”); reconstruction of ideas on sovereignty, title to territory and the like, as conceived in the past.

b) present facts

Examples: the wish of a population (self-determination); existing expectations, hopes, aspirations, beliefs, evaluations; conviction of law (“Rechtsbewusstsein”); political, social or humanitarian situations, nationalism; compliance with obligations; scientific facts (configuration of the bottom of the sea, degree of radiation); effect of certain measures (development aid).

c) future facts

Examples: trends (economics, population); statistics.

Here and there the demarcation-lines between the three categories will be blurred as in the case of compliance with international obligations which can refer to a continuous situation of non-compliance in the past as well as in the present, or in cases of state practice, which would refer to past as well as present practice. Similarly, the necessity of making optimal choices between alternatives sometimes requires to consider at the same time facts as they are now and as they will probably change in the near or distant future.

Second classification

a) internal (psychological) facts

Examples: wishes, expectations, hopes, convictions, beliefs and evaluations among groups, as listed in the first classification mainly sub b).

b) external facts

Examples: past events; words and other signs used and received among interested parties as listed in the first classification sub a); situations, conduct or behaviour, facts of nature and man, effects, trends and probabilities, as listed in the first classification sub b) and c).

Here again the distinction between a) and b) will be blurred, for instance in the case that ideas manifest themselves in external acts such as protests, demonstrations, revolutions and the like”.

14. In the Eastern Greenland Case (P.C.I.J., ser. A/B, No. 53) the effect had to be examined of a suggestion by the Danish Minister at Christiania to the Norwegian Government not to make difficulties in the settlement of the question of the Danish Government extending their political and economic interests to the whole of Greenland, and answered by the Norwegian Minister of Foreign Affairs Ihlen replying that the Norwegian Government would not make any difficulties in the settlement of this question. Suy, , Les actes juridiques unilatéraux en droit international public, 1962, p. 124Google Scholar considers the declaration as part of an agreement and subscribes in this respect to Anzilotti's dissenting opinion (loc. cit. p. 91), but the Court itself refers to the binding undertaking involved in the Ihlen declaration as a “promise” (loc. cit. p. 73).

15. Mavromatis Case (P.C.I.J., ser. A, No. 5); Case concerning certain German interests in Polish Upper Silesia (Merits) (P.C.I.J., ser. A, No. 7). Other examples discussed in Suy, op.cit., pp. 131–140.

16. J. Berteling, Juridical aspects of the pledging conferences of U.N.D.P.; unpublished paper for the master's degree in the political and social sciences at the University of Amsterdam, 1971.

17. In the case concerning the interpretation of the air transport services agreement between the United States and France the Arbitral Tribunal decided (28 December 1963, 16 R.I.A.A. p. 65) that the French authorities by approving the timetables proposed by the American side gave their “implicit consent” to the deviation from the original agreement. The resulting implicit agreement was “constantly confirmed by the attitude of the … [French] authorities throughout the years that followed” (Ibid. p. 70).

18. “… as all the Governments concerned in the present dispute have signed and ratified both the Treaty of Versailles and the definitive Statute, they cannot, as between themselves, contend that some of its provisions are void as being outside the mandate given to the Danube Commission under Article 349 of the Treaty of Versailles” (P.C.I.J., ser. B, No. 14, p. 23). The passage is quoted by Judge Alfaro in his separate opinion appended to the Judgement of the I.C.J. in the Temple Case (I.C.J. Rep. 1962, p. 44) as an application of the principle of estoppel. Bowett, in his study on “Estoppel before international Tribunals and its relation to Acquiescence” (33 BYIL (1957) pp. 176–202 at p. 185)Google Scholar, refers to the Canevaro Case before the Permanent Court of Arbitration. Here especially the claimant's standing as a candidate for the Senate of Peru where none were admitted except Peruvian citizens, and similar acts “unequivocal in their implication”, enabled Peru to regard the claimant as a Peruvian citizen.

19. Advisory opinion concerning the Interpretation of Peace Treaties, I.C.J. Rep. 1950, p. 65.

20. In the Corfu Channel Case the I.C.J., without using the term, considered the statement of one of the parties that a claim for reparation should be a subject of an expert opinion, as an “implied acceptance of the Court's jurisdiction to decide this question” (I.C.J. Rep. 1949, p.25).

21. Electricity Company of Sofia and Bulgaria, P.C.I.J., ser. A/B, No. 79, p. 199.

22. “There are classic doubts about the possibility of tacit consent; here non-verbal performance occurs in an alternative form of performative act…”. J.L. Austin, loc.cit. p. 80.

23. “The Commission noted that in municipal systems of law this principle [ acquiescence in the validity of an agreement that is later challenged ] has its own particular manifestations reflecting technical features of the particular system. It felt that these technical features of the principle in municipal law might not necessarily be appropriate for the application of the principle in international law. For this reason it preferred to avoid the use of such municipal law terms as ‘estoppel’”. Commentary of the International Law Commission on its draft Article 42 which eventually became Art. 45 of the Vienna Convention on the Law of Treaties, Report of the International Law Commission on the work of its eighteenth session, I.L.C. Yearbook 1966 Vol. II pp. 172 ff, at p. 239. See however the I.C.J. in the North Sea Continental Shelf Cases, I.C.J. Rep. 1968, p. 26.

^23a.. In the non-philosophical sense of valuable properties which, in the eyes of the appraising persons, naturally belong to the model, in contrast to properties attached to it in virtue of its origin.

24. “… dans le droit des gens, c'est un principe bien établi, qu'il faut s'abstenir autant que possible de modifier l'état des choses existant de fait depuis longtemps” Grisbadarna Case, Scott, , Hague Court Reports, 1916, p. 493.Google Scholar

25. “fulfilling the requirements of justice and the considerations of utility”, River Oder Case, P.C.I.J., ser. A, No. 23, p. 27.

26. Unless it becomes relevant to the revocability or modifiability of rights arising for third. States from treaties. The assent of the third State has then the effect of putting the expansion of its legal position on a contractual basis (Cf. Art. 37, para. 2 of the Convention on the Law of Treaties, 1969).

27. Wheaton, , Elements of international law, vol. 1 (6th. ed., 1929) p. 336Google Scholar: “This rule is founded upon the supposition, confirmed by constant experience, that every person will naturally seek to enjoy that which belongs to him; and the inference fairly to be drawn from his silence and neglect, of the original defect of his title, or his intention to relinquish it”.

28. Ending with the controversial rules on arbitral procedure in 1958. Law-making declarations of the G.A. should be considered separately from its codification-practice.

29. Report of the Committee of Jurists appointed by the League of Nations Council with respect to the Aaland Islands dispute; Official Journal, October 1920, Spec. Supp. No. 3.

30. I.C.J. Rep. 1950 p. 153.

31. I.C.J. Rep. 1962, p. 168. Lauterpacht, E., “The legal effect of illegal acts of international organisations”, in: Essays in honour of Lord McNair, pp. 88–121Google Scholar; Conforti, B., “The legal effect of non-compliance with rules of procedure of the U.N. General Assembly and Security Council, 63 A.J.I.L. (1969) pp. 479–503.Google Scholar

32. Kunz, , “The nature of customary international law”, 47 A.J.I.L. (1953) p. 667Google Scholar. As far as the modification of treaties by subsequent practice is concerned the U.N. Conference on the Law of Treaties dropped the relevant draft Article 38 of the International Law Commission. United Nations Conference on the Law of Treaties, first session, 26 March-24 May 1968, official records, A/Conf-39/11 p. 215.

33. P.C.I.J., ser. B, No. 14, 1927, pp. 17,27.

34. Johnson, D.H.N., “Acquisitive prescription in international law”, 27 B.Y.I.L. (1950) pp. 332–354Google Scholar; Pinto, M.R., “La prescription en droit international”, 87 Hague Recueil (1955–1951) pp. 391–455Google Scholar; Verykios, P.A., La prescription en droit international public, 1934.Google Scholar

35. “It is incumbent on the Members of the League of Nations not to recognize any situation, treaty or agreement which may be brought about by means contrary to the Covenant of the League of Nations or to the Pact of Paris”. Resolution adopted by the League Assembly on March 11, 1932 in connection with the Manchurian “incident”. Cf. also Lauterpacht, H., “Sovereignty over submarine areas”, 27 B.Y.I.L. (1950) at pp. 397–398.Google Scholar

36. “But the Government of Nicaragua was silent when it ought to have spoken”. Costarican Nicaragua Boundary Case, Moore, , International Arbitrations Vol. 2, p. 1961; 33 B.Y.I.L. (1957) p. 198.Google Scholar

37. Anticipatory protest in connection with no more then reports of local newspapers and current rumours on anti-foreign measures: see MacGibbon, , “Some observations on the part of protest in international law”, 30 B.Y.I.L. (1953) at p. 301.Google Scholar

38. For a similar comprehensive approach, see Schachter, , “Towards a theory of international obligation”, 8 Virginia J.I.L. (1968) at p. 309.Google Scholar

39. “If with respect of any of these territories the Four Powers are unable to agree upon their disposal within one year from the coming into force of the Treaty of Peace with Italy, the matter shall be referred to the General Assembly of the United Nations for a recommendation, and the Four Powers agree to accept the recommendation and to take appropriate measures for giving effect to it”, para. 3 of Annex XI to the Italian Peace Treaty, 1947, 49 U.N.T.S. p. 215.

40. “All States shall observe faithfully and strictly the provisions of … the present Declaration…”. Declaration on the Granting of Independence to Colonial Countries and Peoples, Res. 1514 (XV) of the U.N. General Assembly.

41. Such as the fact that, on one of the Minquiers islands claimed by the United Kingdom, the construction of a house by a French national was stopped after an unanswered protest from the U.K. to the French Government. Minquiers and Ecrehos Case, I.C.J. Rep. 1953, pp. 71,72.

42. Same case, loc.cit. p. 71, and the individual opinion of Judge Basdevant, loc.cit. p. 80.

43. North Sea Continental Shelf Cases, I.C.J. Rep. 1969, para. 73.

44. Thus, in his dissenting opinion appended to the International Court's decision in the Temple Case (I.C.J. Rep. 1962, p. 128) Judge Spender paid attention to the fact that in the early part of this century Siam was apprehensive about the aspirations of France. This was given as the reason why the Thai Government was not asked to protest about the presence at the Temple of a French officer in full military uniform. This lack of protest was among the facts which, in the view of the Court, amounted to “tacit recognition” by Siam of the sovereignty of Cambodia (under French Protectorate) over the Temple area (loc.cit. pp. 30,31).

See also the award in J.H. Williams v. Venezuela:

“There are so many things that may induce one government not to press pending demands against another, disconnected with the demands themselves, consideration for the condition and welfare of the debtor state itself being prominent among them, that we are disposed to think the true and, so far as we are advised, the usual way is to regard time in such cases, in the absence of circumstances evincing abandonment, as no respector of persons.”

Moore, , International Arbitrations, p. 4199Google Scholar; B.Y.I.L. (1934) p. 88.

45. Many cases besides the notorious Fisheries Case, in MacGibbon, op.cit., part III.

46. Cf. Quincy, Wright, in 32 A.J.I.L. (1938) pp. 526–535.Google Scholar

The 1898 Treaty of Paris by which Spain ceded to the United States all rights of sovereignty in the region to which the Island of Palmas belonged remained only a potential menace to the established Dutch sovereignty over the island and did not even require a reaction from the Netherlands to the notification of the treaty. In the words of the arbitrator Max, Huber: “it would be entirely contrary to the principles laid down above as to territorial sovereignty to suppose that such sovereignty could be affected by the mere silence of the territorial sovereign as regards a treaty which has been notified to him and which seems to dispose of his territory”. 2 R.I.A.A. p. 843.Google Scholar

47. “… l'efficacité réclamée est en raison inverse de la valeur du droit violé: plus cette valeur est grande pour la partie qui proteste, plus il est improbable que celle-ci y renoncera et plus on pourra facilement, semble-t-il, conclure à sa volonté de maintenir la règle juridique qui assure la protection du droit en question; par contre, lorsqu'il s'agit d'un droit de peu de valeur et qu'il n'est pas protesté efficacement, on est plutôt fondé, semble-t-il, à conclure que l'Etat qui proteste n'attache pas grande importance à la conservation de ce droit”. Brüel, E., “La protestation en droit international”, 3 Acta scandinavica juris gentium (1932) at p. 87.Google Scholar

48. Grundzüge des positiven Völkerrechts, 3rd ed., 1926, p. 109.Google Scholar

49. Meuse Case, P.C.I.J. ser., A/B, No. 70, p. 25.

50. Other cases in MacGibbon's, pioneering article, “The scope of acquiescence in international law”, 31 B.Y.I.L. (1954) p. 143 ff, at p. 163.Google Scholar

51. Singer, M.G., Generalization in Ethics (1963).Google Scholar

52. Quod maior pars curiae effecit pro eo habetur, ac si omnes egerint (Scaevola L, 19 D. ad municipalem 56, 1).

53. Berger, Encyclopedic Dictionary of Roman Law, p. 665.

54. As Professor Guggenheim has rightly pointed out in connection with the Case concerning Passage over Indian Territory (I.C.J. Rep. 1960 p. 6), if there would have been opinio iuris among the participants of a local practice, they could easily have concluded an agreement on the right of passage. In the case of a multilateral practice, on the other hand, the failure of an agreement may be due to political difficulties and would prove nothing against an inner conviction of the participants as to their practice being law. The author's conclusion is that the existing practice between the parties was non-binding usus, and not bilateral custom as the Court held it to be. Guggenheim, P., “Lokales Gewohnheitsrecht”, 11 Oesterreichische Zeitschrift für öffentliches Recht (1961) p. 332 ff.Google Scholar

55. I.C.J. Rep. 1960, p. 23. See also the dissenting opinion of Judge Tanaka appended to the Judgment of the I.C.J. in the South West Africa Cases, Second Phase, I.C.J. Rep. 1966, p. 297: “The principle of the protection of human rights is derived from the concept of man as a person and his relationship with society which cannot be separated from universal human nature. The existence of human rights does not depend on the will of a State; neither internally on its law or on any other legislative measure, nor internationally on treaty or custom, in which the express or tacit will of a State constitutes the essential element.”

56. “No State has the right to use or permit the use of its territory in such a manner as to cause injury by fumes in or to the territory of another or the properties or persons therein, when the case is of serious consequence and the injury is established by clear and convincing evidence”. Trail Smelter Case, 3 R.I.A.A. p. 1965. See also the statement of the present author during the 1075th meeting of the International Law Commission, I.L.C. Yearbook 1970 vol. I p. 185.

57. Schwelb, E., “Some aspects of international ius cogens as formulated by the I.L.C.”, 61 A.J.I.L. (1967) p. 957.Google Scholar

58. First (Red Cross) Convention, Art. 63(4); Sea Red Cross Convention, Art. 62(4); Prisoners of War Convention, Art. 142(4); Civilians Convention, Art. 158(4); 75 U.N.T.S. p. 2 ff.

59. Which reads: “A treaty is void if, at the time of its conclusion, it conflicts with a peremptory norm of general international law. For the purpose of the present Convention, a peremptory norm of general international law is a norm accepted and recognized by the international community of States as a whole as a norm from which no derogation is permitted and which can be modified only by a subsequent norm of general international law having the same character.”

60. I.L.C. Yearbook 1966 vol. II, p. 248, where the following examples of violations of ius cogens are mentioned: unlawful use of force, trade in slaves, piracy, genocide and, generally, international crimes and violations of human rights. But the principles of self-determination and equality of States were also mentioned as possible examples.

61. “Si, dans la très grande majorité elles n'engendrent que du droit dispositif, il en est toujours quelques-unes, à la vérité peu nombreuses, mais suprêmes parce qu'essentielles, que les Etats qui participent à un certain ordre ne peuvent méconnaftre même dans leurs rapports mutuels. Les normes dites ‘impératives’ qui en procèdent reposent sur une opinio juris qui les place dans une catégorie supérieure, leur autorité l'emportant sur celle des normes ordinaires tenues pour simplement ‘obligatoires’. La norme coutumière se construit sur une pratique; la norme impérative procède directement d'un jugement de valeur morale ou sociale. Seules ces normes indérogeables, valables en dehors de tout lien conventionnel représentent le jus cogens. Sans être susceptibles d'une vraie définition, elles apparaissent liées à un ordre public international. On peut les considérer comme ‘l'expression la plus parfaite du droit international général’ [ Virally]”. Ch. de Visscher, , “Positivisme et jus cogens”, 75 R.G.D.I.P. (1971) p. 5 ff at p. 9.Google Scholar

62. The Supreme Court of the United States, examining the legality or otherwise of the Slave Trade, stated in The Antelope in 1825, that it was “contrary to the law of nature”, but added: “Whatever may be the answer of a moralist to this question, a jurist must search for its legal solution, in those principles of action which are sanctioned by the usages, the national acts, and the general assent, of that portion of the world of which he considers himself a part, and to whose law the appeal is made. If we resort to this standard as the test of international law, the question … is decided in favour of the legality of the trade. Both Europe and America have embarked in it; and for nearly two centuries, it was carried on without opposition, and without censure. A jurist could not say that a practice thus supported was illegal” (As quoted by MacGibbon, , “Customary International Law and Acquiescence” in 33 B.Y.I.L. (1957) p. 115 ff, at p. 143.Google Scholar