1. Introduction

In an article entitled "On the exercise of enforcement jurisdiction in the seas around the Senkaku Islands" in Vol. 3 Issue 1 of the Journal of Island Studies, I had the opportunity to argue incidetally that there was no justification under international law for China's claim to sovereignty over the Senkaku Islands. In doing so, I very briefly pointed out that China had failed to protest against the incorporation of the islands into Japanese territory on the basis of a Cabinet decision of 1895 and suddenly started to claim sovereignty three-quarters of a century later in the 1970s. I then argued that this belated protest had no significance under international law, and that the protracted absence of protest now precludes China from claiming sovereignty, based on the principle of estoppel.

In this paper I would try to elaborate on this argument in terms of international law on the acquisition of title to territory in general, and then to discuss its implications for the Senkaku Islands problem in particular[1]. In the process, I will examine a number of questions; specifically, what significance protest has in international law, what significance an absence of protest (i.e. silence) has, whether the fact of territorial possession has notoriety, to what extent must a fact be known to achieve notoriety, what the possessing state must do to achieve notoriety, and whether third states are responsible for not knowing the fact.

2. Protest, acquiescence, prescription

In the relations between states, the acquisition of title to territory is regulated by a number of factors. When the state claiming possession bases its claim on historical evidence, the questions arise as to whether or not a protest has been made against the claim before a certain amount of time has passed, and whether or not that protest has obstructed the establishment of the title in question. When a state encounters a situation that could cause harm or disadvantageous effects to itself, it intuitively lodges a protest. Thus in the process of acquiring title to territory, it is not unusual that a protest is taken up as an important obstructing factor. Indeed in the relations between sovereign states protest constitutes a formal objection by which the protesting state makes it known that it does not recognize the legality of the acts against which the protest is directed, that it does not acquiesce in the situation which such acts have created or threaten to create, and that it has no intention of abandoning its own rights in the premises[2]. Protest has been generally accepted by writers on international law as a means of preventing the maturing of a prescriptive or historic title.[3]

Here, before proceeding to the next phase of discussion, it would seem appropriate to give a brief indication of the technical distinction between "prescription" and "occupation". Prescription presupposes another state's title to the territory in question, and subsequent adverse acquisition of it during a certain period of time. Occupation, on the other hand, takes place in respect of terra nullius ("no one's land"). In prescription, an acquiescence of the state prescribed against is of the essence of the process, but occupation of terra nullius results in an immediate title opposable to the whole world[4]. However, there are certain similarities between two modes of acquisition of title to territory, particularly with regard to the acts required to substantiate either form of title, and protests can play an important, if not decisive, role in obstructing the acquisition of the territory[5].

(1) Silence is tantamount to acquiescence

If a state keeps silence in a situation where a protest is duly expected to avoid acquiescing in the legality of an act by another state, such silence may perhaps be interpreted as acquiescence. In other words, protest is a means to rebut the presumption of acquiescence. A state is under no obligation to protest, but in circumstances in which failure to protest is tantamount to acquiescence, protest is necessary to preserve the rights of the protesting state[6].

Under certain circumstances, the silence kept by a state can be interpreted as amounting to no more than indifference or self-restraint in formulating any expression of will[7], but writers are nearly unanimous in emphasizing the importance of formulating a protest in some form[8].

To have a look at a few international arbitrations on this point, in the Alaska Boundary Arbitration of 1903 counsel for the United States asserted that, had Great Britain believed her rights to be infringed or endangered, she would have protested rather than "permit a claim of this sort to pass unchallenged, and grow into a right, or at least something by which a right can be perfected."[9]

Again, in the Colombia/Venezuela Frontier Arbitration of 1922, Colombia successfully argued before the Arbitrator by relying on the failure of Venezuela to protest on two relevant occasions when a protest would have been expected if Venezuela had believed her rights to be affected. The Arbitrator ruled that "[l]'absence de protestation est, en droit international, une des formes de l'acceptation ou de la reconnaissance de certains faits" ("In international law, the absence of protest is one form of acceptance or recognition of certain facts")[10].

Similarly, in the Guatemala/Honduras Borders case of 1933 the Arbitral Tribunal found in its Award:
"If it had been considered that Honduras was being deprived of territory to which she was entitled, and especially that Guatemala was asserting authority over territory which was, or prior to independence had been, under the administrative control of Honduras, it can hardly be doubted that these assertions by Guatemala would have aroused immediate antagonism and would have been followed by protest and opposition on the part of Honduras. The intense feeling existing at the time, and the natural jealousy of the new States with respect to their territorial rights, would have caused a prompt reaction. But it does not appear that such protest was made or that opposing action was taken by Honduras."[11]

Turning to relatively recent cases, in the Anglo-Norwegian Fisheries case of 1951, the UK agent argued that governments protest "in order to make it quite clear that they have not acquiesced and to prevent a prescriptive case being built up against them."[12] Further in the Minquiers and Ecrehos case"of 1953 counsel for the UK observed that "the exact legal effect of a protest depends very much on circumstances, but in general all it does is to register or record the opinion of the protesting country that the act protested against is invalid and is not acquiesced in."[13] The limitations of protest are indicated here[14].

What seems to have been an inadvertent failure to protest in the past did in fact cause a major effect in the Anglo-French Continental Shelf Delimitation case of 1977. In the phase of drawing a median line between the British and French coasts in the English Channel, the United Kingdom asserted that Eddystone Rock, like the other promontories on its south coasts, should be the base-point from which the median line should be measured. As the Rock is some eight nautical miles off the coast, its choice as the base-point would have caused the median line to swerve significantly toward the French coast. However, the Court of Arbitration found in favour of the UK position on the ground that France had acknowledged the use of the Rock by the UK Government as the base-point in establishing its fishery limits under the European Fisheries Convention of 1964. The Court stated:
"[I]t was in the context of a baseline of the territorial sea, as well as in the context of fisheries, that the French Republic in 1964-1965 acknowledged the relevance of the Eddystone Rock as a base-point."[5]

To put it another way, the Eddystone Rock was chosen not just for the functional purpose of the fishing zone but as a base-point for setting the basic territorial sea baseline, and France was adjudged to have, if inadvertently, acquiesced in it. Consequently, France was not permitted to oppose the use of the Rock as a basepoint. This could be seen as an example of the application of the principle of estoppel.

In the recent ICJ jurisprudence on territorial and boundary dispute cases, effectivités (effective acts) are often examined in response to the requests of the parties, and in this process, whether protest was lodged against such acts presented as effectivités is considered. For example, in the Territorial and Maritime Dispute case (Merits) between Nicaragua and Colombia of 2012, in which Colombia asserted that it had been conducting effectivités over a series of maritime features like islets and cays near the Nicaraguan coasts, on the premise that it had sovereignty over those features based on a 1928 treaty, the Court recognized the failure of Nicaragua to protest and ruled as follows:
"It has thus been established that for many decades Colombia continuously and consistently acted à titre de souverain in respect of the maritime features in dispute. This exercise of sovereign authority was public and there is no evidence that it met with any protest from Nicaragua prior to the critical date. Moreover, the evidence of Colombia's acts of administration with respect to the islands is in contrast to the absence of any evidence of acts à titre de souverain on the part of Nicaragua.
The Court concludes that the facts reviewed above provide very strong support for Colombia's claim of sovereignty over the maritime features in dispute."[16]

In a domestic context, the Supreme Court of the United States judged long-term inaction to signify acquiescence in the State of Arkansas v. State of Tennessee case of 1940. On the status of disputed land arising as a result of "avulsion" (natural separation) of a river, the Special Master stated:
"There is no showing that Arkansas ever asserted any claim to the land in controversy prior to the institution of this suit. The lands were never surveyed or granted by Arkansas."[17]

Based on this, the Supreme Court ruled that
"The contentions of Arkansas in opposition to the application of the principle of prescription and acquiescence in determining the boundary between states cannot be sustained. That principle has had repeated recognition by this court. ... Applying this principle in Indiana v. Kentucky ... to the long acquiescence in the exercise by Kentucky of dominion and jurisdiction over the land there in controversy, the court said: 'It is a principle of public law universally recognized, that long acquiescence in the possession of territory and in the exercise of dominion and sovereignty over it, is conclusive of the nation's title and rightful authority."[18]

Admittedly this is a domestic case, but the rationale here is the same as in international judicial decisions.

Unlike these cases, there are others that appraise protest positively. In the Chamizal Arbitration between the United States and Mexico of 1911, the dispute was over the attribution of the Chamizal Tract, formed by the flooding of the Rio Grande that flows between the two countries. The United States advanced the contention that it had acquired, in addition to its title under treaty provisions, a good title to the tract of land in dispute by prescription grounded on possession of the territory maintained without disturbance, interruption or challenge. However, the three commissioners (Arbitrators) were unanimous in coming to the conclusion that "the physical possession taken by citizens of the United States and the political control exercised by the local and Federal Governments have been constantly challenged and questioned by the Republic of Mexico, through its accredited diplomatic agents," and thus that "the possession of the United States in the present case was not of such a character as to found a prescriptive title."[19] The decision goes on to state:
"In the present case, the Mexican claim was asserted before the International Boundary Commission within a reasonable time after it commenced to exercise its functions, and prior to that date the Mexican Government had done all that could be reasonably required of it by way of protest against the alleged encroachment."[20]

On the issue of Mexico not having taken more forceful acts, the Award states: "However much the Mexicans may have desired to take physical possession of the district, the result of any attempt to do so would have provoked scenes of violence and the Republic of Mexico cannot be blamed for resorting to the milder forms of protest contained in its diplomatic correspondence."[21]

It thus positively recognized the value of protest.

The next question that could arise is whether a diplomatic protest is forceful enough to produce an actual effect of preventing the claimant state from acquiring title. Protest would at least draw the attention of international public opinion to the issue. One writer suggests, however, that it serves as a warning to the claimant state that its pretensions will not go unchallenged, but he admits on the other hand that a protest not followed by other action will become in time "academic" and "useless"[22]. The "other action" that used to be required was some kind of forceful opposition. But such forceful opposition is of no avail today[23].

Another writer suggests that since 1919 reference of the matter to the League of Nations or the Permanent Court of International Justice and since 1945 to the United Nations or the International Court of Justice could be the "other action" to follow up a protest. He goes on to say that "[t]he result is that the diplomatic protest is of reduced significance and is certainly not now the principal method of interrupting prescription. A protest since 1919 can be said to have amounted to no more than a temporary bar."[24] This assumes that such a third-party settlement mechanism can function well enough,[25] and looks a little too optimistic a view, because some states, including the coastal states in the East Asian seas, still do not seem to subscribe to third-party settlement of disputes. Under these circumstances, diplomatic protest may not be sufficiently forceful, but failure to protest in a situation where protest is due to the objecting state could not be interpreted otherwise than as amounting to the abandonment of its claim to title.

(2) Notoriety and ignorance

As discussed above, failure to protest when it is necessary is generally interpreted as acquiescence, but there are situations in which silence does not necessarily signify consent or acquiescence. A state cannot protest without knowledge of a circumstance which may endanger its interests or infringe on its rights. In this sense knowledge is a prerequisite for acquiescence. There is, therefore, some authority for the view that publicity of an alleged occupation is a requirement of international law.[26], but the major opinion seems to be that publicity is not a requirement[27].

Some writers say that possession on which prescriptive title rests must satisfy the requirement of notoriety. Fauchille, for example, points out that only on the condition of notoriety a state against which the possession operates can make its view known. Although it is at first sight difficult to imagine a clandestine adverse possession remaining for long unknown to the owner, it is, nevertheless possible in the case of territories which are either distant or of slight importance[28]. Johnson stresses publicity as a condition for prescription, saying:
"Acquisitive prescription depends upon acquiescence, express or implied.[29] Acquiescence is often implied, in the interests of international order, in cases where it does not genuinely exist, but without knowledge there can be no acquiescence at all."[30]

On the other hand, there is some difficulty in disproving knowledge. In the Minquiers and Ecrehos case, France sought to justify her failure to protest against the British acts of sovereignty over the islets for sixty years by saying that "it was impossible for France to keep the United Kingdom Government continually under surveillance", but Judge Carneiro, in his Individual Opinion, commented:
"[The French Government] should have kept the islets under surveillance, just as the British Government had done. ... Failure to exercise such surveillance and ignorance of what was going on in the islets indicate that France was not exercising sovereignty in that area."[31]

In the 1951 Anglo-Norwegian Fisheries case, the International Court of Justice ruled that:
"[t]he notoriety of the facts, ... Great Britain's position in the North Sea, her own interest in the question, and her prolonged abstention would in any case warrant Norway's enforcement of her (straight baseline) system against the United Kingdom."[32]

However, the dissenting judges were clearly of the opinion that the alleged facts and circumstances were not such that knowledge of the existence and extent of the system could or ought to be imputed to the United Kingdom, and such knowledge they held to be essential to the binding force of an historic title. Judge Sir Arnold McNair, having examined the asserted Norwegian straight baseline system, stated that "[i]n the circumstances, I do not consider that the United Kingdom was aware, or ought but for default on her part to have become aware, of the existence of a Norwegian system of long straight base-lines connecting outermost points, before this dispute began in 1906 or 1911."[33] Judge Read, in his dissent, had this to say:
"It is impossible to overlook the fact that the evidence clearly indicates that the Government of the United Kingdom had no actual knowledge of the Norwegian System, or of the nature and extent of the rights claimed by Norway. ... [N]o information was given to the Government of the United Kingdom, at any time before the commencement of the dispute, that could be regarded as actual or constructive notice that Norway was asserting the right to establish a belt of territorial waters measured from long base-lines departing from the line of the coast."[34]

On the other hand, if knowledge is overemphasized, it might be misused to allege that the failure to protest was a result of the lack of knowledge. This could give rise to the question whether a formal notification of claims to foreign states is required under international law. There seems to be little authority for the view that an actual or formal notification is necessary[35]. The Award in the 1928 Island of Palmas case" did not require official notification of a claim for its validity:
"A clandestine exercise of State authority over an inhabited territory during a considerable length of time would seem to be impossible. An obligation for the Netherlands to notify to other Powers the establishment of suzerainty over the Sangi States or of the display of sovereignty in these territories did not exist. Such notification, like any other formal act, can only be the condition of legality as a consequence of an explicit rule of law. A rule of this kind adopted by the Powers in 1885 for the African continent does not apply de plano to other regions."[36]

It was assumed by the Arbitrator that if the display of sovereignty is continuous and peaceful over a sufficiently long period of time, the fact could ensure a notoriety of the possession of the territory in question[37]. Similarly, the arbitral tribunal in the 1931 Clipperton Island case also held official notification unnecessary:
"La régularité de l'occupation française a aussi été mise en doute parce qu'elle n'a pas été notifiée aux autres Puissances. Mais il faut observer que l'obligation précise de cette notification a été stipulée par l'art. 34 de l'acte de Berlin précité, qui, comme il a été dit plus haut, n'est pas appliquable au cas présent. Il y a lieu d'estimer que la notoriété donnée d'une façon quelconque à l'acte suffisait alors et que la France a provoqué cette notoriété en publiant l'acte même de la manière sus-indiquée."[38]
(The legitimacy of the occupation by France has also come into doubt because she did not notify the other Powers. But it should be observed that the actual obligation to make such notification was stipulated in Article 34 of the Berlin Protocol noted above, ... which is not applicable to the present case. There are sufficient grounds to consider that the notoriety attributed to the act, by whatever means, was sufficient at the time, and that France provoked this notoriety by publicizing that act in the manner indicated above.)

Since the Clipperton Island case"[39], no writer seems to have argued that occupation should be formally notified[40]. In fact, A. Ross says that "formal declaration or notification of occupation is not required, but of course is often to be recommended by way of proof."[41] According to one writer, it may even be dispensed with altogether[42].

Nevertheless, certain concern remains about whether notification is necessary or not. When discussing territorial waters, Johnson says:
"States are often ignorant of each other's legislation in the matter of territorial waters. Even a maritime State, such as the United Kingdom, had no knowledge of some of the Decrees of other States put in as evidence by Norway during the proceedings."[43]

This kind of ignorance seems true to some extent, as is shown in the French reply to the United States enquiry about its attitude to the series of continental shelf legislation of certain Latin American countries following the Truman Proclamation of 1945:
"Le gouvernement francais n'a jamais recu, par la voie diplomatique, notifications des resolutions ou propositions adoptées, de 1945 à 1950, par la Mexique, le Chili, le Pérou, Costa Rica et le Salvador, ayant pour effet de changer la limite de leurs eaux territoriales."[44]
(The French government has never received, through diplomatic channels, notifications of resolutions or propositions adopted from 1945 to 1950, by Mexico, Chile, Peru, Costa Rica and El Salvador for the purpose of changing the limits of their territorial waters.)

It may be asked if such ignorant states have to be deprived of their rights under international law without clear evidence of express acquiescence in a territorial claim of another state. The crucial question here is whether their silence means acquiescence. In today's world of advanced communications, it is hard to think that a territorial claim of a state can go quite unnoticed. In other words, a claim cannot go unnoticed to other states, particularly those in the neighborhood whose interests may be affected thereby. Unlike in those days mentioned above, there is no room for doubt about notoriety today. Therefore, it would be hard to avoid the conclusion that ignorance as to another state's territorial claim, extending over a certain period of time, can be fatal. This is so not only as a matter of fact but also as a matter of law: failure to protest when protest is due under the circumstances could indirectly help the claimant state to establish title to the territory in question, and the state which has thus failed to protest would be prohibited under the principle of estoppel from claiming title to that territory thereafter. This leads on to an examination of the principle of estoppel.

(3) The principle of estoppel

The principle of estoppel is originally a private law concept forming part of the Anglo-American law of evidence. It has been defined as follows:
"Where one by his word or conduct willfully causes another to believe in the existence of a certain state of things, and induces him to act on that belief so as to alter his previous position, the former is concluded from averring against the latter a different state of things as existing at the same time."[45]

The principle underlying estoppel is said to be recognized by all systems of private law[46], and could thus be seen as one of "general principles of law". Several arbitrations have recognized this. For example, in the British Guiana/Venezuela Boundary Dispute case of 1899, when Venezuela asserted that the United Kingdom, having accepted the so-called Palmerston Line of 1850, might not claim any territory beyond it, neither the UK nor the tribunal denied the admissibility of estoppel as between states.[47]

It should also be noted that estoppel is not only a technical rule of evidence in Anglo-American law but also has been found to be a principle of substantive law under international law[48].

In the Legal Status of Eastern Greenland case", the Permanent Court of International Justice pointed out that Norway had recognized the whole of Greenland as belonging to Denmark, and ruled that "[T]hereby she (i.e. Norway) has debarred herself from contesting Danish sovereignty over the whole of Greenland."[49] The Court also found, to the same effect, that "there can be no ground for holding that ... it is estopped from claiming ... that Denmark possesses an old established sovereignty over all Greenland."[50] In the Temple of Preah Vihear case of 1962 estoppel was discussed in some detail in respect of a map. Since Thailand once recognized the map as valid, it was held not to be allowed subsequently to deny it.
"Even if there were any doubt as to Siam's acceptance of the map in 1908, and hence of the frontier indicated thereon, the Court would consider, in the light of the subsequent course of events, that Thailand is now precluded by her conduct from asserting that she did not accept it. She has, for fifty years, enjoyed such benefits as the Treaty of 1904 conferred on her, if only the benefit of a stable frontier. France, and through her Cambodia, relied on Thailand's acceptance of the map. ... It is not now open to Thailand, while continuing to claim and enjoy the benefits of the (border) settlement, to deny that she was ever a consenting party to it."[51]

Estoppel was very briefly discussed in the Land, Island and Maritime Frontier Case between El Salvador and Honduras (Nicaragua intervening) of 1990 before the Chamber of the International Court of Justice[52], while in the Libya/Chad Territorial Dispute case"of 1994, Judge Ajibola in his Individual Opinion cited the Alaska Boundary case"of 1903, the Delagoa Bay case"of 1875, the Guatemala-Honduras Borders Arbitration of 1933, the Grisbadarna case"of 1909 and the Island of Palmas case"of 1928, and stated:
"There are many awards of international tribunals also supporting the principles of estoppel or acquiescence in the sense of silence or absence of protest."[53]

Here, only arbitral awards are cited, but as has been show above, discussions on the principle of estoppel are also found in the jurisprudence of the Permanent Court of International Justice and the International Court of Justice.

Thus, considerable importance seems to have been given to estoppel by writers and in international arbitral and judicial decisions. Indeed parties tend to resort to this principle, if not explicitly, when they criticize the conduct of the opponent parties in international litigations. For example, in the North Sea Continental Shelf cases of 1969, the Federal Republic of Germany (West Germany) had signed but not ratified the 1958 Convention on the Continental Shelf, and was therefore not bound by the boundary delimitation rules in Article 6 of the Convention. However, the other parties (Netherlands and Denmark) argued that West Germany had in fact accepted the rules of Article 6 in its course of conduct. That is, West Germany made no formal declaration of opposition to Article 6 at the Geneva Conference, signed the Convention with no reservations made to the provisions of Article 6, at one point expressed an intention to ratify the Convention, and has appeared to rely on or at least referred to certain provisions of the Convention in its official pronouncements on the continental shelf rights. They argued that since they had handled their affairs on that understanding, West Germany was now bound by the provisions of Article 6, and particularly by the principle of equidistance. This was clearly an attempt to apply the principle of estoppel to West Germany, but the Court observed that none of the circumstances cited by Denmark and the Netherlands was decisive or definitive, that they were capable of various interpretations and explanations, and concluded that West Germany could not be assumed to have accepted the system of Article 6 as a binding one[54]. In other words, the Court denied estoppel, but the parties had used it as a tool for criticizing the other party. Such a use of estoppel is not rare; a similar argument of estoppel was propounded in the Gulf of Maine case of 1984 between the United States and Canada.[55]

This is a phenomenon that cannot be ignored as an instance of state practice. This principle has now reached the point where it might be reasonably regarded as established under international law. So what happens when it is applied to the Senkaku Islands problem? This question will now be examined.

3. Implications for the Senkaku Islands problem

There used to be no dispute between Japan and China over the Senkaku Islands until the early 1970s. The Japanese government conducted a very careful study to see whether any state had sovereignty over the islands, and having confirmed that no state had claimed sovereignty, incorporated them into Ishigaki City, Okinawa Prefecture by a Cabinet decision in January 1895. In legal terms, this was an "occupation" of terra nullius ("no one's land"). No foreign state made any protest against this incorporation at the time nor thereafter, until a scientific report disclosed potential of oil and natural gas deposits in the seas around the islands in May 1969. The Committee for Co-ordination of Joint Prospecting for Mineral Resources in Asian Offshore Areas (CCOP), a body under the aegis of the United Nations Economic Commission for Asia and the Far East (ECAFE), conducted a series of seismic surveys in this sea area in the autumn of 1968, and published the results the following May. The CCOP report revealed a surprising estimate that there was a highly likely potential of oil and natural gas in this sea area, equivalent to that of the Persian Gulf region in the Middle East[56], and coupled with the 　finding of the International Court of Justice in the North Sea Continental Shelf cases in February of the same year that "natural prolongation" under sea of the land mass of the coastal state entitles it to the continental shelf and natural resources on it, caused a stir among the coastal states in the East China Sea about the desire for oil and gas. Thereupon Japan, South Korea and Taiwan started negotiating ways and means of exploring for and exploiting oil and gas in this sea area, when China suddenly broke its silence on the legal status of the Senkaku Islands towards the end of 1970 and began to make moves of its own.[57]

Yet on at least two earlier occasions China had failed to claim sovereignty over the islands. A news article that appeared on 8 January 1953 in the People's Daily, the official organ of the Chinese Communist Party, hinted that China considered the Senkaku Islands to belong to Japan, for it reported, using the Japanese names for the relevant islands and islets:
"The Ryukyu Islands scatter to the north-east of our Taiwan and to the south-west of Kyushu, Japan, including the seven island groups of Senkaku Islands, Sakishima Islands, Daito Islands, Okinawa Islands, Ohshima Islands, Tokara Islands, and Ohsumi Islands. ..."[58] (Emphasis added)

This is a part of the report that the people of the Ryukyu Islands were struggling to protest against the United States occupation, a context which had nothing to do with the ownership of those islets[59]. This unguarded description may be interpreted as unconsciously revealing China's honest admission of Japan's ownership of the islands. Again, when China issued declaration of an administrative nature on the breadth of its territorial sea on 4 September 1958, it missed the opportunity to express an intention of owning the Senkaku Islands. The declaration stated:
"The breadth of the territorial sea of the People's Republic of China shall be twelve miles. This provision applies to all the territories of the People's Republic of China, including the Chinese mainland and its coastal islands, as well as Taiwan and its surrounding islands, the Penghu Islands, the Dongsha Islands, the Xisha Islands, the Zhongsha Islands, the Nansha Islands and all other islands belonging to China which are separated from the mainland and its coastal islands by the high seas."[60]

The declaration listed all the islands over which China claimed sovereignty, but failed to mention the Senkaku (in Chinese: Diaoyu) Islands by name. Should a strained interpretation be allowed of this provision, it may possibly be reasoned that the islands were included in "Taiwan and its surrounding islands" or "all other islands belonging to China"[61], but the distance between the Senkaku Islands and Taiwan is several times greater than that between the Pescadores (the Penghu Islands) and Taiwan, making such an interpretation hard to swallow. Above all, if the islands were so important as to be called a "core interest" today, the notion that they were included among "Taiwan and its surrounding islands" or "all other islands belonging to China" without being specified by name is a highly ridiculous interpretation. It is hard to imagine China, a state known to be extremely sensitive about territorial issues in particular, doing something so stupid. In other words, there is no other way but to conclude that after all, even at this point, China had no awareness that the Senkaku Islands were Chinese territory.

Additionally a few Chinese maps show the Senkaku Islands as Japanese territory, but it is proposed here not to play them up. For in international judicial decisions and among expert geographers, rather negative assessment has been made of the question of whether maps accurately show the ownership of territory. In the Burkina Faso/Mali Frontier Dispute case of 1986, the International Court of Justice found that maps in themselves cannot create title to territory but can only have significance when used as a physical expression of a state's intentions in the form of annexes as an integral part of official documents[62]. This evaluation has since been acceded to at least in several cases[63], and is supported by geographers [64].

Thus, while it seems to have taken the Senkaku Islands as Japanese for a long time, China all of a sudden began to claim title to the islands towards the end of 1970 in reaction to the CCOP survey mentioned above that indicated the potential of oil and natural gas in the sea areas around the islands. Then in February 1992, perhaps because it had realized that it had weak legal grounds for its claim to title, China enacted the "Law on the Territorial Sea and the Contiguous Zone", in which it identified Diaoyu as part of its state territory for the first time in history[65]. On top of it, China then started asserting that the islands were among its "core interests", comparable in importance to Taiwan and others[66]. Viewed objectively, this attitude seems to suggest a shift in "policy" so that the state can get whatever it wants. States are free to make this kind of "policy" change, which is not particularly surprising in itself. However, if such a policy change infringes on the rights of a neighboring state, it cannot be overlooked nor tolerated because it is illegal and runs counter to the norms of the international community.

As stated at some length in the previous section, states are obliged to protest as a minimum required measure when confronted with situations that are disadvantageous to them or endanger their rights. If they fail to do so, they forfeit the right to make claims. With respect to the Senkaku Islands problem, China should have protested against Japan's explicit incorporation of the islands into Japanese territory in 1895, if it had suffered disadvantage or her sovereignty had been violated at all. Even after that, although it presumably had opportunities to protest, China continued to fail to protest for another three-quarters of a century until the aforementioned CCOP report. To assess this continued failure in legal terms, there is no other way but to characterize China's attitude as "acquiescence" in Japan's territorial sovereignty over the Senkaku Islands during this long period.

Even if, for the sake of argument, China had indeed had its alleged "historic title", such a claim might only have held true in a medieval sense. As international law is law, it evolves. Evolved modern international law regards "effective control" as the decisive factor in the acquisition of territory. The incorporation of the Senkaku Islands into Japanese territory by a Cabinet decision of 1895 and the various subsequent administrative measures constitute effective control by Japan over those islands. If this were to be called a violation of China's sovereignty, China should have duly raised a voice in protest, but failed to do so[67]. This is an undeniable fact.

However that may be, China did in fact fail to make a "protest" as a minimum required act of opposition or resistance to Japan's incorporation measure[68]. The fact of this protracted negligence is by no means insignificant in legal terms. For, as a result of this negligence, China has forfeited the right it may hypothetically have had[69]. To assert the right now would be against the principle of estoppel.

4. Conclusion

The acquisition of territory does not materialize if it is opposed by foreign states. Though there are various ways in which foreign states can express their opposition, diplomatic protest is a common and minimum expression of opposition. It is a common knowledge of the international community that failure to protest is interpreted as acquiescence, which has a legal effect under international law. This function of acquiescence means a loss of grounds to claim title to the territory in question, and claiming title anew is legally prohibited under the principle of estoppel. It follows, therefore, that China is no longer entitled to claim sovereignty over the Senkaku Islands.

On 28 June 2014 China's President and Communist Party General Secretary Xi Jinping gave a speech at a conference to commemorate the 60th anniversary of the 1954 "Five Principles of Peaceful Coexistence" in Beijing. In the speech, he said: "To build a new type of international relations, we should uphold fairness and justice," and urged the international community to "jointly promote the rule of law in international relations." He also urged that all states "abide by international law and well-recognized basic principles governing international relations and use widely applicable rules to tell right from wrong and pursue peace and development."[70] To put it briefly, he emphasized "the rule of law" and "observance of international law" in the international community.

This is a truly laudable speech, and this author welcomes it. While statements made by leaders of democratic nations like Japan are not necessarily of a normative nature and have no binding force on the citizens, in China that is governed by the Communist Party's one-party rule statements by the Party General Secretary and President are understood to have a normative function and universal binding force, with the result that anyone disobeying them is to be punished. Consequently, such statements are expected to have an extremely powerful impact.

In reality, however, China is engaged in a variety of provocative acts in contradiction to President Xi's statements: building artificial islands near several tiny reefs and sandbars in the seas of the Spratly Islands in the South China Sea, over which sovereignty is being disputed with some other states, or reclaiming land around those reefs and sandbars to build bases of supplies for ships and runways for aircraft[71]. China's explanation is that as the sea areas surrounded by the so-called "Nine-Dash Line" [72], including the islands inside it, are historically within China's sphere of sovereignty, China is free to undertake construction works there without interference from foreign states. However, such a claim has not been recognized under international law, nor should it be.

If the argument of the neighboring states against the mentioned Chinese acts were equally not clearly recognized under international law, it would follow that there is an international territorial dispute, which must be dealt with on the basis of international law as expounded by President Xi. In this process, historic grounds for the territorial claims and the past communications between the parties to the dispute would have to be examined, while the presence or absence of protest or the state of acquiescence would have to be ascertained at the same time. This is precisely the application and observance of international law or the rule of law. Avoiding these reliable but time-consuming procedures forcefully to materialize one's own claims is nothing other than a revival of the past evil foreign policy of "Macht geht vor Recht (Might before Right)".

In the Xi speech mentioned above, he said "We should jointly uphold the authority and sanctity of international law and the international order. All countries should exercise their rights in accordance with the law, oppose bending international law, and reject any attempt to undermine, in the name of the 'rule of law', other countries' legitimate rights and interests as well as peace and stability."[73] Very well said, indeed. But in view of the fact a foreign policy in contradiction to these statements is currently being enforced, it is hard to get rid of a sense of astonishment and doubt as to what his speech was meant for.[74]