|Consent, Estoppel, And Reasonableness: Three Challenges To Universal International Law, by Anthony D'Amato, 10 Virginia Journal of International Law 1 (1969)
[Note that this text is set up so that the footnotes applying to an individual page appear at the foot of the page rather than at the end of the document.]
Although a very important part of international law is made up of rules found in treaties, conventions, executive agreements and contracts among nations, the usual image conjured up by the phrase "international law" is that of a body of rules that apply, or should apply, to all states irrespective of their explicit consent or "sovereign will" of the moment. If law were dependent merely upon each state's will, then there could be no violation of the law and the term would be fictitious.
Something close to fictionalization of universal rules of international law has appeared in the writings of several prominent scholars who deal with general customary law. For their theories of consent, estoppel, and reasonableness come very close to conditioning, if they do not actually condition, the validity of international law upon the wishes of the "defendant" state. While some degree of acquiescence of the member states of a system is necessary to the continued effective functioning of the system, a state will from time to time have to comply with norms with which it may not agree. Further inadequacies of these theories are their single-factored explanation of the source of obligation in international law and their reliance upon a single intellectual task, logical deduction.
Nevertheless, these theories-when they are actually applicable-do have a definite psychological appeal which adds to the felt pressure of international law on the "defendant." The present paper is an attempt to distinguish, and to show the importance of distinguishing, between these logical and psychological positions.
The idea that a state is not "bound" by a rule of international law unless it had previously "consented" to that rule is an extreme form of the positivist tradition in international jurisprudence which flourished in the nineteenth century. Its proponents, who in Lauterpacht's words had an "exaggerated regard for sovereignty", FN1 tried to explain custom as merely a tacit treaty, entered into by all the states which
FN1. Lauterpacht, Decisions of Municipal Courts as a Source of International Law, 10 BRIT. Y. B. INT'L L. 65, 83 (1929).
[page 2] had consented to the given rules. FN2 In recent years this position has found important advocates among Soviet jurists who have seized upon the notion of strict consent as a way either to reject "capitalist" norms or simply, in Professor Lissitzyn's words, "to pick and choose among the norms of international law." FN3 One of the leading spokesmen of the Soviet position, Professor Tunkin, has written that "agreement is the essence of custom" in that it expresses the "will of a State" to "consent" to a rule and thus become bound by it. FN4 Some non-Soviet writers have also concluded that consent is at the basis of custom. MacGibbon, for example, attempts to explain the fundamental dilemma of custom (that an act is formative of custom if it is undertaken with a conviction that it is already required by international law) by focusing upon consent and acquiescence. If a state does not protest the actions of other states, MacGibbon argues that the acquiescence implied by this failure to protest
seems necessarily to involve the further otiose conviction that participants in the course of conduct are entitled to act as they are doing; and this in turn appears to leave little alternative to submission in the belief that submission is obligatory . FN5
In 1954 Judge Fitzmaurice reached the same conclusion in a more moderately worded statement that has been frequently quoted:
Where a general rule of customary international law is built up by the common practice of States, although it may be a little unnecessary to have recourse to the notion of agreement (and a little difficult to detect it in what is often the uncoordinated, independent, if similar, action of States), it is probably true to say that consent is latent in the mutual tolerations that allow the practice to be built up at all; and actually patent in the eventual acceptance (even if tacit) of the practice, as constituting a binding rule of law . FN6
All of these views share common ground in the belief that international law does not exist unless the individual state agrees that it shall exist, and that therefore an individual state is not bound by anything that it has not consented to. The leading case on customary
FN2. For a more recent restatement of this position, see Corbett, The Consent of States and the Sources of the Law of Nations, 6 BRIT. Y. B. INT'L L. 20, 22-25 (1925).
FN3. 0. LISSITZYN, INTERNATIONAL LAW TODAY AND TOMORROW 55 (1965).
FN4. Tunkin, Co-Existence and International Law, 95 ACADEMIE DE DROIT INTER- NATIONAL, THE HAGUE, RECUEIL DES COURS [RECUEIL DES COURS] 3, 13 (1958).
FN5. MacGibbon, Customary International Law and Acquiescence, 33 BRIT. Y. B. INT'L L. 115, 131 (1957).
FN6. Fitzmaurice, The Law and Procedure of the International Court of Justice, 1951-54: General Principles and Sources of Law, 30 BRIT. Y. B. INT'L L. 1, 68 (1953).
[page 3] law seems at first glance to corroborate this position. The World Court in the Lotus Case held that
International law governs relations between independent States. The rules of law binding upon States therefore emanate from their own free will as expressed in conventions or by usages generally accepted as expressing principles of law and established in order to regulate the relations between these co-existing independent communities or with a view to the achievement of common aims. FN7
However, on closer inspection, the statement in the Lotus Case may be seen to stand more for a limitation on the idea of consent than a reinforcement of it. The Court was careful to talk about aggregate consent; the terms are specified in the plural and not in the singular. This is a significant point even though it seems not to have been particularly noticed by writers on consent or custom. For it is in fact harmless to speak of aggregate consent; it is a truism that international law is the creation of all the states. From a functional point of view, the only difficulty arises when a claim is made that each individual state-indeed, the defendant state in any given controversy-must itself have consented to a rule in order to make the rule binding upon it. One writer who focused upon the distinction between aggregate and particular consent was Professor Jaffe, who in 1933 wrote that "consent is given to international law as a system rather than 'to each and every relationship contained in it." FN8
The Lotus Case made it clear that neither France nor Turkey was going to prevail because of any notion of particular consent. Rather, the decision turned on whether customary law was created in four previous municipal-court cases, only two of which involved French vessels and none of which involved a Turkish vessel. FN9 The World Court has had numerous occasions to apply customary international law, and yet nowhere has it held as a matter of general customary law that the defendant state must have consented to the rule in question in order to be bound by it. The Court has no doubt recognized the importance of the general observation that the very existence of international law in international claim-conflict situations is at stake in this question of consent. If the only way a defendant state can be held accountable to law is by proving that that state consented to the particular rule in question, hardly any case could ever be won by a plaintiff state. Indeed, most disputes arise precisely because the disputing states have not specifically consented to the rule at issue. Since the facts of international state behavior demonstrate the continuing relevance of legal arguments based upon custom, and since the
FN7. Case of the S. S. "Lotus,"  P.C.I.J., ser. A, No.9, at 4, 18.
FN8. L. JAFFE, JUDICIAL ASPECTS OF FOREIGN RELA11ONS 90 (1933).
FN9. Case of the S.S. "Lotus,"  P.C.I.J., ser. A, No.9, at 28-29.
[page 4] World Court and all other international tribunals have been able upon occasion to reach decisions against defendant states in the absence of proof that the defendants had consented to the rules claimed by the plaintiffs, Professor Jaffe's observation seems to be the only possible conclusion. By the fact of their engaging in international legal argumentation, or by virtue of their claims of the benefits of international rules relating to boundaries or shared resources, all states have in fact consented to the international legal system-not to each and every rule in it, but to the secondary rules of law-formation and the generally accepted mode of legal argumentation and legal standards of relevance. This consent is, after all, a manifestation of the self- interest of states to settle a significant number of their international disputes by law, or to avoid frictions that would otherwise be present if that law depended in each application upon the consent of the state objecting to the particular application.
A more detailed look at state practice strengthens the validity of these observations. First, one would suspect that, if the particular consent theory were valid, new states would typically engage in the practice of making a list of all the international norms they want and of rejecting the others. But no state has ever done this. Nor have the existing states ever asked a new state, upon its entry into the family of nations, to consent to existing rules of law. Indeed, it appears to be a general rule of law, as Lauterpacht pointed out, that a new state "cannot repudiate a single rule." FN10 Of course, what this means is that a purported repudiation would not be given legal effect by the other states, not that a new state lacks the physical ability to repudiate a rule.
Further, if new states wanted to repudiate existing rules, a convenient opportunity would be when subject to suit in an international tribunal. But Professor Waldock observed in 1962:
Nor has any State ever argued before the [World] Court that it was exempt from a general customary rule simply because it was a new State that objected to the rule. In the Right of Passage case, for example, it never occurred to India to meet Portugal's contention as to a general customary right of passage to enclaves by saying that she was a new State; nor did Poland, new-born after the First World War, ever make such a claim in any of her many cases before the Permanent Court. FN11
This is not to say that the new states have all accepted all the existing rules of international law with enthusiasm. On the contrary, as Professor Lissitzyn has shown, many of the new states resent their
FN10. H. LAUTERPACHT, PRIVATE LAW SOURCES AND ANALOGIES OF INTERNATIONAL LAW 53 (1927).
FN11. Waldock, General Course on Public Internatwnal Law, 106 Rec. des Cours (Neth.) 1, 52 (1962).
[page 5] colonial past and assert that some rules, such as those relating to expropriation, are not binding upon them. FN12 Nevertheless, their attitude even to rules of expropriation has not in practice been extremist; as Professor Lissitzyn has also pointed out, when occasions arose for the new nations to support Communist proposals on expropriation of foreign investments, many did not lend their support. FN13
Broadly speaking, Professor Waldock's observation seems true: "the new States have at least as much to lose as anyone else from a denial of the validity of existing international law." FN14 Rather than trying to set up specific exemptions for themselves, which would be an espousal of the consent doctrine, the new states have chosen to express support of international law while at the same time working to help change the content of that law so as better to reflect the needs of the growing numbers of new states. They are working particularly in the field of treaties and General Assembly resolutions, as pointed out by Professor Bishop in his Hague lectures of 1965, to change the content of substantive rules. FN15 Even Professor Tunkin, who attempts to maintain a strict individual consent or "doctrine of agreement" approach, has conceded that
if a new state enters without reservations into official relations with other states, this means that it recognizes a certain body of principles and norms of existing international law, which constitute the basic principles of international relations. FN16
Since no new state has entered with reservations, and since Professor Tunkin has not, and could not, proclaim which "basic principles" the new states have, in some unstated manner, “recognized," perhaps even Professor Tunkin might be included among those who really mean by the consent theory the aggregate consent of all the states to the international legal system and not particular consent to each and every substantive rule within the system.
A second example of state practice that does violence to the "doctrine of agreement" supports Kelsen's argument that if an existing state acquires for the first time an access to the sea, that state immediately becomes subject to all the norms of international law regarding conduct of states on the seas, without there being any attempt on the part of other states to secure its consent or efforts by the acquiring state to pick and choose among the norms with which it agrees. FN17 We
FN12. 0. LISSITZYN, supra note 3, at 73-89.
FN13. Id. at 103.
FN14. Waldock, supra note 11, at 52.
FN15. Bishop, General Course of Public International Law, 115 Rec. des Cours (Neth.) 147, 463 (1965).
FN16. Tunkin, Remarks on the Juridical Nature of Customary Norms of International Law, 49 CALIF. L. REV. 419, 428 (1961).
FN17. H. KELSEN, PRINCIPLES OF INTERNATIONAL LAW 114 (R. Tucker transl. 1966).
[page 6] may expect the same result to follow as states in turn acquire the technology to participate in activities in outer space; they will find awaiting them a fairly well developed body of legal rules fashioned primarily by the pioneers.
A third example of state practice which calls into question the concept of particular consent is the remarkable fact that a state's rights and duties in international law, in Professor Lissitzyn's words, "are not impaired by changes in its law, government, or constitutional structure, no matter how violent, at least so long as the core of its territory and population remain the same." FN18 Yet consent, in the sense given by Professors Tunkin, MacGibbon, and Fitzmaurice at the beginning of this chapter, is something that is expressed by particular nation-state officials acting as representatives of their governments. It makes no sense to anthropomorphize "states" to say that a state itself has consented; yet even if the particular individuals who expressed a state's consent are overthrown in a revolution or defeated in the next election, the consent is not revoked. Treaties and contracts persist, as well as the state's obligations to the general body of customary international rules.
Fourth, international law sometimes assumes that a state has consented when in fact it has not. Treaties of peace, for example, are valid even when imposed upon the vanquished state. Moreover, a state is bound by a treaty if it has been entered into on the state's behalf by officials having the apparent authority to bind the state, even if in fact they lacked authority under the state's own constitution. Article 2, section 6, of the United Nations Charter extends certain principles to non-Member states. And the World Court's advisory opinion in the Reservations to the Genocide Convention Case FN19 has signalled a breakdown of the strict consent theory where it had hitherto been thought to be especially applicable-in the matter of defining the parties to a treaty when some of them make reservations not accepted by the others.
Fifth, if the consent theory were truly an expression of an individual state's will to be bound, logic would require that if a state changes its mind it would cease to be bound. But international law has consistently given the opposite answer. Thus, for example, a state cannot get rid of its treaty obligations by passing contrary municipal laws.
Finally, it is interesting to note that in a recent study of state practice as expressed primarily through domestic judicial interpretations of international obligations, Professor Falk concludes that the alleged requirement of presumed consent in customary law must be dropped. FN20 Consent is a vertical verbal rationalization that in Professor
FN18. 0. LISSITZYN, supra note 3, at 10.
FN19. Advisory Opinion on Reservations to the Genocide Convention,  I.C.J. 15.
FN20. K. FALK, THE ROLE OF DOMESTIC COURTS IN THE INTERNATIONAL LEGAL ORDER 171 (1964).
[page 7] Falk's analysis does not accord with the primarily horizontal ordering of authority and power among independent and relatively equal states in the international system. This conception appears to be closer to the meaning of the authoritativeness of custom than Professor Tunkin's solipsistic doctrine of agreement.
When a single term such as "consent" raises such logical difficulties, the temptation arises to resort to a kindred term to mask some of the problems. Thus, the concept of "acquiescence" has recently become fashionable. But it is difficult to distinguish meaningfully between consent and acquiescence, and especially between implied consent and acquiescence.
In situations where these terms are interchangeable, the notion of acquiescence would be subject to the same infirmities as that of consent. Writers who have attempted to expand the notion of ac- quiescence to cover situations falling short of implied consent add no strength to the concept. MacGibbon, for example, defines acquiescence as "silence or absence of protest in circumstances which generally call for a positive reaction signifying an objection." FN21 But this is an ambiguous formula. While it embraces certain clear situations which indeed "call for" an expression of protest (for instance, an attack on an embassy abroad), it also includes many other situations in which a state refrains from protesting another state's actions or omissions because the protest will be ineffective and only serve to annoy the other state. For example, many states may deplore France's nuclear test series in the Pacific Ocean, particularly in light of the Limited Nuclear Test Ban Treaty, which most states have signed; yet only a few states have formally protested France's actions. FN22 Their silence need not amount to acquiescence, but may rather be attributable to a realistic political assessment that a diplomatic protest would not deter France in the slightest but might only serve to worsen relations with France. On the other hand, there may exist situations where a state issues a formal note of protest but, by failing to take further steps, has in fact acquiesced. This could occur, for example, when a state expropriates a foreign-owned mining company that had paid below-par salaries to local workers and had shipped all profits abroad. The foreign state may issue a formal diplomatic note of protest on behalf of its national whose property was confiscated, perhaps because of the pressure exerted domestically by that national, and may nevertheless "let it be understood" informally that it is sympathetic with the act of expropriation. From these and many other possible situations, it is evident that there is no warrant for assuming that a state's silence or failure to protest is the equivalent of acquiescence.
This conclusion is apparent from the situations MacGibbon himself
FN21. MacGibbon, The Scope of Acquiescence in International Law, 31 BRIT. Y. B. INT'L L. 143 (1954).
FN22. See D'Amato, Legal Aspects of the French Nuclear Tests, 61 AM. J. INT'L L. 66-67, 76 (1967).
[page 8] cites. His examples prove at most that there is non-acquiescence when a state protests; they do not prove the converse, that discrete circumstances might be defined which "call for" protest. FN23 For it is very difficult, except in certain clear situations where states normally protest certain types of acts, to say that protest is "called for" by the circumstances. Further, it is nearly impossible to say it in a situation that might create a new rule of international law or change an old rule; for such a situation, by definition, will have no precedents with respect to the practice of protest. In sum, MacGibbon's definition and use of the concept of acquiescence amount to finding acquiescence whenever states are silent. This, in turn, amounts to presumed acquiescence, which is not an analytically useful concept but merely another cumbersome legal fiction.
The vagueness of the term "acquiescence" may account for its use in a related but different sense, worth examining briefly. This is the notion of acquiescence not solely on the part of the state directly affected by the actions or omissions of another, but on the part of the community of states in general. Judge Hudson's fourth criterion necessary for the emergence of a customary rule of law, set forth in a draft prepared for the International Law Commission, is "general acquiescence in the practice by other States." FN24 Similarly, Judge Fitzmaurice wrote of the effect of consent "in the eventual acceptance (even if tacit) of the practice, as constituting a binding rule of law." FN25 It is evident that what these writers have in mind is the truism that international law is only that which is recognized as such in the consensus of states. If a given rule, or the practice giving rise to a rule, meets with objection by the overwhelming majority of states-not simply verbal objection or notes of protest, but a complete unwillingness to recognize that rule in all relevant claim-conflict situations-then by definition that rule is not a rule of international law.
International law is that law which is manifested in the practice of all or most of the states; in this sense, it is the law that is generally accepted or "acquiesced in" by the international community. But in functional terms, the notion of acceptance or acquiescence does not normally help us decide what the rules in the international legal system in fact are. For only a very few rules can be cited that have actually been "acquiesced in" by explicit expression on the part of the preponderance of states. The great bulk of primary rules in all their detail owe their existence directly to the workings of the secondary rules of law-formation, which themselves are the manifestations of the use by states of international legal techniques in their claim-conflict
FN23. See MacGibbon, supra notes 5, 21; MacGibbon, Some Observations on the Part of Protest in International Law, 30 BRIT. Y. B. INT'L L. 293 (1953).
FN24. Hudson, Working Paper on Article 24 of the Statute of the International Law Commission,  2 Y. B. INT'L L. COMM'N 24, 26, U.N. Doc. A/CN. 4/16 (1950).
FN25. Fitzmaurice, supra note 6, at 68.
[page 9] situations. It is somewhat misleading to condition the validity of primary rules upon the acquiescence of other states, for the acquiescence does not relate to the primary rules but rather to the propriety of the processes (the secondary rules) by which the primary rules were created. Thus, the concepts of consent and acquiescence tend to become superfluous when they concern general community attitudes. To say that the community of states has acquiesced is simply to say that the rule is a valid rule of international law. This was indeed indirectly acknowledged by Judge Fitzmaurice six years after he wrote the passage previously cited. As Special Rapporteur to the International Law Commission's study on treaties, he noted that all States can be deemed to consent to rules embodied in treaties when such rules gain general-currency in international customary law. FN26 By thus imputing consent to the states, Fitzmaurice attests to its analytic uselessness.
Despite all the analytical difficulties involved in attempts to find consent or one of its permutations as the basis for customary law, it is nevertheless important to recognize the psychological importance of the role played by consent in reinforcing the authoritativeness of custom. The fact that some states do consent to some rules, the fact that some instances clearly amount to acquiescence, the fact that many international acts are the result of mutual tolerances, and even the increasing importance of treaties (which are clear cases of consent) in the body of international rules, all add to the acceptability of customary rules of international law. Government officials newly in power, for instance, often find it convenient to explain to their constituents that the state cannot do certain international acts because the state itself, through previous government officials, had agreed not to do so. The feeling of having previously consented to something is a powerful curb on desires to do something else. Hobbes recognized this in his attempt to show that citizens had constructively consented to the powers of the Leviathan, and Burke carried the process even farther by arguing that ancestral consent to the constitution binds the present inhabitants of a state. Apart from the merits of these political theories, their very existence and fame attest to the psychological importance people attach to the idea of consent. In international litigation, the attempt is invariably made to find some sort of evidence that the opponent state at one time consented to the rule it now opposes. In the Status of Eastern Greenland Case, for example, a mere verbal remark by one foreign minister to another was given critical importance in establishing one country's consent to the other's sovereignty in Greenland. FN27 But the frequency of recourse to arguments about prior consent does not establish the necessity of proving consent in
FN26. Fitzmaurice, (Fifth) Report on the Law of Treaties,  2 Y. B. INT'L L. COMM'N 69, 94-96, U.N. Doc. A/CN. 4/130 (1960).
FN27. Case of the Legal Status of Eastern Greenland,  P.C.I.J., ser. A/B, No.53, at 22, 57-58.
[page 10] each alleged instance of a customary rule; rather it illustrates the psychological importance of consent, with respect to some rules or to the international legal system as a whole, that reinforces the authoritativeness of any customary rule.