Atsuko Kanehara

Reconsideration of the Distinction between the Use of Armsin Law Enforcement and the Use of Force Prohibitedby International Law―With an Analysis of the Inherent Significance ofThis Issue to Japan―
Atsuko Kanehara*
Abstract
This article examines the distinction between the use of arms in law enforcement and theuse of force prohibited by international law with some analysis thereof having inherent
significance to Japan in its particular context in the East China Sea. Following on from theprevious work by this author, entitled “The Use of Force in Maritime Security and the Useof Arms in Law Enforcement under the Current Wide Understanding of Maritime Security,”
published in this Journal, reconsideration of the distinction is strongly required. This isbecause the already wide understanding of maritime security is expanding even further.
As a result, two kinds of distinctions tend to be blurred, namely, the distinction between
security or military acts and law enforcement, on the one hand, and also, the distinction
between the use of arms in law enforcement and the use of force prohibited by internationallaw, on the other hand. This is typically the case with Japan, which has been facing, as aninherent circumstance, the continued tension in the East China Sea.
The structure of this article is as follows. After clarification of the terminology of thisauthor, the Introduction will provide, in the particular circumstance surrounding Japan,
concrete reflection of the issue of the two distinctions mentioned here. Then, Section I will,based upon said previous work by this author, succinctly confirm the presupposition thatthe nature of acts or measures, in principle, decides the nature of the use of force or arms
accompanying said acts or measures. Some complementary arguments will follow. Section
II will consider several issues arising from the presupposition that this article maintains.
Within the framework of the analysis thus provided, Section III will explore how to provea use of weapons as a use of arms in law enforcement. For this purpose, this article will
examine the relevant jurisprudence, mainly focusing on those recently entertained rather
than those traditionally discussed, and will list up as many critical factors as possible thatneed to be carefully considered, together with their possible categorization. In Section IV
and Section V, as an examination of a special issue, some analysis will follow regarding law
enforcement measures with weapons implemented by Japan to cope with Chinese vessels in
the East China Sea. Finally, some conclusion will be given.

* Atsuko Kanehara is Professor of Public International Law at Sophia University.
** All URLs were last accessed on the 24th of December 2022.

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Reconsideration of the Distinction between the Use of Arms in Law Enforcement
and the Use of Force Prohibited by International Law—With an Analysis of the Inherent Significance of This Issue to Japan—

Introduction

A

1. Terminology
t the beginning of this examination, some explanation of the terminology is necessary
to avoid any confusion. Different from the expression “the physical use of weapons,”1
according to the relevant international law rules, “the use of force” and “the use ofarms” have legal connotations. The expression “the use of force” is used as a legal
term to connote a legal meaning. This is because the term “the use of force” or simply “force” ispart of Article 2, Paragraph 4 of the United Nations Charter (UN Charter), and the rule in thisprovision has been established as a customary international law rule.
In the same way, the term “the use of arms,” as exercised in law enforcement measuresthat could be defined by international law rules, may gain a legal connotation.2 There is specialparlance in regard to the law of the sea, such as the right to approach, the right to recognize thenationality of a vessel, and the right to visit (boarding inspection). In place of them, this article
uses the generic and general term “law enforcement.”
When appropriate and necessary, the expression “situation” will be used in the manner defined
as follows. “Situations” refer to various sorts of scenes or stages in law enforcement measures andmilitary acts. There is a “self-defense situation,” where military acts are expected with the use offorce prohibited by international law.3 The situation in which law enforcement measures are to betaken is called a “law enforcement situation.” The nature of a particular situation is presupposed
to be the same as that of the acts or measures to be conducted or taken in said situation.4 It is notalways easy to make the distinction between concrete acts and the context thereof, namely, the“situation” in which the acts are conducted. Therefore, the distinction between “acts or measures”
and the “situation” inevitably becomes a relative one.
In order to avoid redundant repetition, when no confusion is expected, in this article, “theuse of force” means the use of force prohibited by international law unless being justified
principally as an exercise of the right of self-defense, and “the use of arms” means the use of arms
accompanying (or, in conjunction with, and in connection with, etc.) law enforcement measures.
With this terminology, then, the remaining par t of the Introduction will explain thecircumstance inherent to Japan. In doing so, given the wide understanding of maritime security,
the concrete definition of the issues of the two kinds of distinctions mentioned above will beclarified, and its significance will be proven.

2. Concrete Definition of the Two Issues of the Two Kinds of Distinctions under
the Wide Understanding of Maritime Security
It is well recognized that the idea of maritime security has expanded to include combat,
in addition to militar y threats, various threats including terrorism, weapon proliferation,1“Forcible acts” and violence also mean acts with weapons. This paper will use the expression “thephysical use of weapons” or simply “the use of weapons.”2

A clear and established definition of law enforcement is difficult to find under international law. This
article will take up this issue later.

3“Aggression,” “invasion into territories of foreign States,” and “the right of self-defense” are the typicalterms used to describe such a situation. Under the law of armed conflict, a certain circumstance isdefined as an armed conflict. In that case, the circumstance is legally defined as an armed conflict, andthere is no need for the term “situation.”

4

While it is not clearly demonstrated, one author seems to take the same position as that of thisarticle: Patricia Jimenez Kwast, “Maritime Law Enforcement and the Use of Force: Reflections on theCategorisation of Forcible Action at Sea in the Light of the Guyana/Suriname Award,” Journal of Conflict& Security Law, 13 (2008), 63.

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Atsuko Kaneharatransnational crimes, piracy, environmental/resource destruction and illegal seaborne migration,and so on.5 There would be no argument that this tendency has developed further, considering
the fact that recently, there have been international conflicts regarding the seizure of foreign
vessels,6 and serious incidents such as illegal, unreported and unregulated (IUU) fishing, marine
environmental harm, and piracy and armed robbery. So, it may be useful here to (re-)examine
the significance of the wide understanding of maritime security. This point can be explained in acontext particular to Japan.
First of all, in 2018, Japan enacted the Third Basic Plan on Ocean Policy (Basic Plan)7 andadopted as its main pillar the idea of comprehensive maritime security.8 The reason for the
adoption of such an idea as comprehensive maritime security is set forth as follows.9
Substantively speaking, various ocean policies are closely related to each other, and theyshould form an essential part of the comprehensive policy of maritime security.10 In addition,
as a background unique to Japan, the idea of comprehensive maritime security was and stillis expected to push for ward the procedural development of the organizational structure of
the bureaucracy for both drafting and realizing Japanʼs ocean policy. In order to enact suchcomprehensive ocean policies, an integrated structure of ocean policy-making should beestablished that is apart from the traditional vertically segmented organizational structure of thebureaucracy in Japan.11
Regarding the content of comprehensive maritime security, the Basic Plan contains two
categories of policies for maritime security: policies for maritime security, and policies forming
the foundation for contributing to maritime security.12 The former, in addition to self-defense
measures, consists of measures such as those for maintaining the peace and order of the oceansby law enforcement, the realization of the safety of marine traffic, and coping with ocean-oriented
5

Typical examples are as follows. Douglas Guilfoyle, “Maritime Law Enforcement Operations andIntelligence in an Age of Maritime Security,” International Law Studies, U.S. Naval War College, 93(2017), 298 et seq.; Natalie Klein, Maritime Security and the Law of the Sea, (Oxford University Press,2011); Atsuko Kanehara, “Japanʼs Ocean Policy and Free and Open Indo-Pacific Strategy,” Lectures
Delivered 25 through 29 of September, 2018, in India, Bangladesh, and Sri Lanka, https://www.in.embjapan.go.jp/itpr_en/00_000740.html, https://www.bd.emb-japan.go.jp/itpr_en/PR20180927.html,
https://www.lk.emb-japan.go.jp/itpr_en/00_000678.html; Atsuko Kanehara, “The Use of Force inMaritime Security and the Use of Arms in Law Enforcement under the Current Wide Understandingof Maritime Security,” Japan Review, 3 (2), Fall (2019), https://www.jiia-jic.jp/en/japanreview/pdf/
JapanReview_Vol3_No2_05_Kanehara.pdf (hereinafter referred to as “Maritime Security”).

6This article will subsequently examine the recent jurisprudence in which the seizure of Ukraine military
vessels by the Russian authorities raised the issue of the distinction between the use of arms in law
enforcement and the use of force accompanying military activities.

7

As a Cabinet Decision, the Japanese government enacted the Third Basic Plan on Ocean Policy (BasicPlan) on 15 May 2018. A provisional English translation is available at https://www8.cao.go.jp/ocean/english/ plan/pdf/plan03_e.pdf.

8

Atsuko Kanehara, “Dai Sanki Kaiyo Kihon Keikaku ga Egaku Anzenhosho no Sugata [Maritime Security
That the Third Basic Plan on Ocean Policy Provides for],” Komei 152 (2018), 22–28.

9“Maritime Security,” 50–51.

10Prior to the Basic Plan, in 2007, Japan enacted the Basic Act on Ocean Policy. A provisional English
translation is available at, https://www.cao8.go.jp/ocean/policies/law/pdf/law_je.pdf.

11Regarding the particular significance of the idea of comprehensive maritime security from the viewpointof Japanʼs organizational structure for ocean policy-making, see the lectures by the author, supra n. 5.

12The policies for combatting illegal acts at sea, such as IUU fishing, terrorism, environmental
destruction, and seaborne natural disaster, are not necessarily based upon the “common” interests ofinternational society. Sovereign States recognize these illegal acts as maritime threats to their “individual”
interests.

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Reconsideration of the Distinction between the Use of Arms in Law Enforcement
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natural disasters.13 The latter is divided into two types of measures: measures forming the basisof maritime security and measures that support it in a complementary manner.14 Such content issufficient proof of the wide coverage of comprehensive maritime security.
The Basic Plan actually includes not only the typical issue of the use of force against military
threats, but also the issue of law enforcement to combat illegal acts committed at sea, suchas piracy, terrorism, illegal migration, IUU fishing, etc.15 From the perspective of this article,
the point is that both sets of policies, for coping with military threats and with illegal acts, areincluded together in the policies on maritime security. This fact reflects Japanʼs position that selfdefense and law enforcement are connected to each other in a unique manner.16 Beyond that, theactual circumstance surrounding Japan in the East China Sea inevitably causes the two issues tobe more closely connected. This forms the second point of the circumstance inherent to Japan.
Second, Japan has been facing, for more than a decade, the seriously tense circumstancecaused by China in the East China Sea.17 The principal background for it is the difference of
opinions between the two countries regarding the territorial sovereignty of the Senkaku Islands.18
To demonstrate its territorial sovereignty over the islands, China has persistently dispatched its
vessels, such as government vessels, military ships, and fishing boats, to the contiguous zone andthe territorial sea of Japan surrounding the Senkaku Islands.19
To cope with the tense circumstance, the Japan Coast Guard (JCG) has unceasingly beenon duty guarding the territorial sea of the Senkaku Islands. This is due to Japanʼs position thatthe tense circumstance should, at least, be primarily coped with by police measures or by law
enforcement measures taken by the JCG. Avoidance of escalation forms the main reason forthat position.20 In actuality, however, it is likely that the circumstance will easily grow to thepoint of creating a militar y threat to Japan, one that could not effectively be handled by the
JCG. The Japan Maritime Self-Defense Force (JMSDF), meanwhile, is in charge of maritime
self-defense. When it is necessar y and the legal requirements under the domestic laws are
satisfied, the JMSDF should take action at the scene. In this regard, under Japanese law, thedistinction between law enforcement measures and self-defense ones must be rigidly maintained.
In particular, under Article 25 of the Coast Guard Law (CGL), 21 the JCG is never considered
13

The Basic Plan, 24–26.

14

These are measures for economic security and protection of the marine environment. The Basic Plan,
28.

15

According to the International Maritime Organization, with regard to the distinction between maritime
safety and maritime security, the latter is related to protection against unlawful and deliberate acts, ascited by Klein, op. cit., supra n. 5, 8, n. 23.

16

This article will elaborate on this point later when it examines Japanʼs position when coping with
Chinese warships and government ships that enjoy immunity.

17

As a detailed explanation for this tense situation, see Atsuko Kanehara, “International Law as a Tool
to Combat China,” Japan Review, 4 (1), Summer (2020), https://www.jiia-jic.jp/en/japanreview/
pdf/04JapanReview_4-1_summer_Kanehara.pdf, 1-3; Atsuko Kanehara, “Refining Japanʼs Integrative
Position on the Territorial Sovereignty of the Senkaku Islands,” International Law Studies, 97 (2021),
https://digital-commons.usnwc.edu/cgi/viewcontent.cgi?ar ticle=2990&context=ils, 1954–1957(hereinafter referred to as “Japanʼs Integrative Position”).

18

As Japanʼs official position does not admit the existence of a dispute, this article does not use the word
“dispute.” See “Japanʼs Integrative Position,” 1591, 1610–1612.

19

A statistical analysis is provided and continuously updated by the Japan Coast Guard, https://www.
kaiho.mlit.go.jp/mission/senkaku/senkaku.html.

20

Kanehara, supra n. 17, 19.

21

An unof ficial English translation of the CGL is available at https://nippon.zaidan.info/
seikabutsu/2001/00500/contents/00021.htm.

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a militar y organ.22 In addition, the JMSDF takes not only defense measures but also police
measures under Article 82 of the Self-Defense Force Law.23 The use of weapons by both the JCG
and the JMSDF, as far as it is for police measures, is restricted as such by Article 7, Paragraph 1of the Police Duties Execution Law.24
Irrespective of the legal and theoretical distinction between the two issues, law enforcement
and self-defense, the reality is that, very naturally and unavoidably, the two issues co-exist andare almost inseparable in the same circumstance. As a result, it becomes very difficult to makethe distinction between the use of arms in law enforcement and the use of force prohibited byinternational law. In other words, if Japan, under its laws,25 tries to strictly maintain the distinction
between the law enforcement measures and self-defense measures, and also between the use of
weapons accompanying each of these two measures, and if Japan insists on the distinction not
only domestically but also internationally, too, it bears the heavy burden of proving, by itself, thenature of the use of weapons, whether it is the use of arms in law enforcement or the use of force
in self-defense.
Such a reality has been further strengthened by Chinaʼs recent enaction of its Coast Guard
Law (CCGL) in 2021.26 Article 83 reads:
Coast guard organizations perform defense operations and other tasks in accordance with the“National Defense Law of the Peopleʼs Republic of China”, the “Peopleʼs Armed Police Law of
the Peopleʼs Republic of China” and other relevant laws, military regulations and orders of theCentral Military Commission.
This provision enables Chinese law enforcement vessels which are dispatched to Japan ʼ s
22Article 25 of the CGL reads:
Nothing contained in this Law shall be construed to permit the Japan Coast Guard or its personnel
to be trained or organized as a military establishment to function as such.

23

This is called a “maritime police operation.” Regarding maritime police operations, see Koichi
Morikawa, “Kaijo Keibi Kodo no Kokusaiho Jo no Konkyo ni Tsuiteno Ichi Kosatsu―Kaijo Jieitai no
Chuto Chiiki Haken wo Meguru Giron wo Tegakarini―[An Analysis of the Maritime Police Operation
under International Law―with the Example of the Discussion on Japanʼs Dispatch of the JMSDF to theMiddle Eastern Region],” in Masaharu Yanagihara, Koichi Morikawa, Atsuko Kanehara, Taro Hamada
eds., Gurobaru Keizai to Kokusaiho Chitsujo, Mamiya Isamu Sensei Tsuito Kinen [International Law
Order and the Global Economy, Memory of Professor Isamu Mamiya], (Shinzansha, 2021), 33 et seq.

24

The provision reads:
In the event that there is probable cause to deem it necessary for the arrest of a criminal or theprevention of a criminalʼs escape, for self-protection or the protection of others, or for suppressionof resistance to the performance of public duty, a police official may use a weapon within the limits
judged reasonably necessary in the situation;
Provided, however, that the police official must not inflict injury upon any person except in a casefalling under Article 36 (Self-Defense) of the Penal Code (Act No. 45, 1907) or Article 37 (Avertingpresent Danger) of the same Act, or a case falling under one of the following items:
An unofficial English translation is available at: https://www.japaneselawtranslation.go.jp/ja/laws/
view/4043/tb. As for4 Article 25 of the CGL, see supra n. 22.

25

Article 9 of the Constitution of Japan and Article 25 of the CGL form the principal part of the relevant
laws. Article 9 of the Constitution of Japan reads:
Aspiring sincerely to an international peace based on justice and order, the Japanese people forever
renounce war as a sovereign right of the nation and the threat or use of force as means of settlinginternational disputes.
An official English translation is available at: https://japan.kantei.go.jp/constitution_and_government/
frame_01/html.

26

An unofficial English translation of the CCGL is available at the U.S. Air University web site: https://www.airuniversity.af.edu/Portals/10/CASI/documents/Translations/2021-02-11%20China_Coast_
Guard_Law_FINAL_English_Changes%20from%20draft.pdf.

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territorial sea surrounding the Senkaku Islands to easily change their function from law
enforcement to self-defense. 27 In the circumstance of these sea areas, from the practicalperspective of an effective response by Japan, the distinction between law enforcement and selfdefense would become significantly fruitless.28
In addition, relating to the distinction between the use of arms and the use of force, while a
detailed examination will be given later, here, it is useful to point out the special issue that Japan
has been facing. For more than a decade, China has periodically sent its government vessels andmilitary ships to Japanʼs territorial sea surrounding the Senkaku Islands.29 They enjoy immunity
under Article 32 of the United Nations Convention on the Law of the Sea (UNCLOS). The JCG
has been incessantly watching Japanʼs territorial sea around the Senkaku Islands, and copingwith Chinese government vessels and military ships on the spot. It is always performing a law
enforcement function, and coast-guarding is an exercise of Japanʼs sovereignty over the islands
with the territorial sea thereof according to the law of the sea, namely, Article 2 of UNCLOS.
If Japan takes coercive measures that are beyond a request to leave under Article 30 of
UNCLOS,30 in some cases even using weapons, many authorities indicate that the stage wouldchange from one under the law of the sea to one regulated by the law relating to the use of force.31
Therefore, here, also, the issue becomes complicated with respect to the distinction between theuse of arms in law enforcement and the use of force prohibited by international law.
Thus far, focusing on the inherent circumstance which Japan has been facing, in a concretemanner, the Introduction has clarified the wide understanding of maritime security. In thatcircumstance, the distinction between the use of arms in law enforcement and the use of force
prohibited by international law can be easily blurred in reality. Japan needs to effectively copewith the circumstance by taking law enforcement measures and self-defense measures with thelegal justification under both its domestic laws and international law.32
Next, Section I will formulate a theoretical framework under which the distinction between
the use of arms in law enforcement and the use of force prohibited by international law isappropriately discussed.
This author has already proposed a theoretical framework in that sense.33 Here, after
confirmation of the framework, some complementary explanation will be provided.

I. A Theoretical Framework for the Analysis of the Distinction between the Useof Arms in Law Enforcement and the Use of Force Prohibited by International
Law
1. Formulation of the Issues to Be Discussed
The distinction between the use of arms and the use of force has begun to attract attention in
27

As to other criticism against the CCGL, see “Japanʼs Integrative Position,” 1625–1626.

28

Regarding the impact of the CCGL on Japan, see Atsuko Kanehara, “The Impact on Japanʼs Coast Guard
and Maritime Security Caused by Chinaʼs Coast Guard Law of 2021,” Japanese Yearbook of InternationalLaw, Vol. 65 (2022), forthcoming.

29

See “Japanʼs Integrative Position,” 1594–1595.

30

Here, the issues of the interpretation of the relevant provisions of UNCLOS and their relationship toeach other, such as Article 30 and Article 32, are not touched upon. This article will do so succinctly
later.

31

The relevant works will be introduced later as appropriate.

32

Sections IV and V will thoroughly examine this point, particularly from the perspective of international
law.

33

“Maritime Security,” 40–49.

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relatively recent days. As for early examples of such jurisprudence, there are the 1998 Fisheries
Jurisdiction Case (jurisdiction)34 entertained by the International Court of Justice (ICJ), and the1999 M/V Saiga Case (No. 2)35 dealt with by the International Tribunal for the Law of the Sea(ITLOS).36 In these cases, with regard to the use of weapons by the law enforcement organsof the defendant, its nature was discussed, that is to say the nature of the use of arms in law
enforcement, not the use of force that falls under Article 2, Paragraph 4 of the UN Charter.
A thorough examination of the relevant jurisprudence will be conducted later, in Section III.
Prior to that, to provide an example of the formulation of the issues to be dealt with in this article,
the following remarks by the court and the tribunal are helpful.
In the Fisheries Case, the ICJ said:
84. For all of these reasons the Court finds that the use of force37 authorized by the Canadianlegislation and regulations falls within the ambit of what is commonly understood as enforcementof conservation and management measures and thus falls under the provisions of paragraph
2 (d) of Canadaʼs declaration. This is so notwithstanding that the reser vation does not interms mention the use of force. Boarding, inspection, arrest and minimum use of force forthose purposes are all contained within the concept of enforcement of conser vation andmanagement measures according to a “natural and reasonable” interpretation of this concept(emphasis added).38
In the Saiga Case, ITLOS said:39
155. In considering the force used by Guinea in the arrest of the Saiga, the Tribunal musttake into account the circumstances of the arrest in the context of the applicable rules ofinternational law. Although the Convention does not contain express provisions on the use offorce in the arrest of ships, international law, which is applicable by virtue of article 293 of theConvention, requires that the use of force must be avoided as far as possible and, where force
is unavoidable, it must not go beyond what is reasonable and necessary in the circumstances.
Considerations of humanity must apply in the law of the sea, as they do in other areas ofinternational law.
156. These principles have been followed over the years in law enforcement operations at sea(emphasis added).
By carefully reading these remarks, there appear two issues: first, the nature of themeasures,40 and second, the nature of the use of weapons (in the expression by the court and thetribunal, “use of force”). In these cases, the nature of the measures is law enforcement, and thenature of the use of weapons is, too, the nature of the use of arms in law enforcement according to
the terminology of this article.41 Beyond that, in these remarks of the jurisprudence, it is difficult
34

Fisheries Jurisdiction (Spain v. Canada), Jurisdiction of the Court, Judgment of 4 December 1998, I.C.J.
Reports 1998, 432 (hereinafter referred to as “the Fisheries Jurisdiction Case”).

35

The M/V “Saiga” (No.2) Case (Saint Vincent and The Grenadines v. Guinea), Judgment of 1. July, 1999,
https://www.itlos.org/fileadmin/itlos/documents/cases/case_no_2/published/C2-J-1_Jul_99.pdf(hereinafter referred to as “the Saiga Case”).

36

Other cases will be introduced later, in Section III, 2.

37

The ICJ and ITLOS may use the expression “use of force” as meaning the physical use of weapons
without necessarily connoting a legal nature. It is important to interpret the judgments depending on
the context of whether or not the expression means the use of force as that falling under Article 2,
Paragraph 4 of the UN Charter.

38

The Fisheries Jurisdiction Case, para. 84.

39

The Saiga Case, paras. 155–156.

40

Hereinafter, where appropriate, to avoid redundancy, “measures” will mean both measures and acts.

41

The court and the tribunal do not make clear these two issues.

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to find a useful theoretical framework for the analysis of this article regarding the distinction
between the use of arms and the use of force. For such an analysis in particular, a theoreticalframework should be required to regulate the relationship between the two issues, namely, theissue of the nature of the measures and the nature of the use of weapons in the measures.

2. Presupposition on the Relationship between the Nature of the Measures andThat of the Use of Weapons: The Presupposition Confirmed
Above all, as to the theoretical framework, this author does not take the position of a sort of caseby-case approach of making distinction between the use of arms and the use of force.42
A case is imagined in which, while measures have the nature of law enforcement, the use of
weapons holds the nature of the use of force that is likely to accompany military measures, and istherefore prohibited by international law. Vice versa, it might be possible that, while the measures
are regarded as military ones, the use of weapons in connection with them is regarded as the useof weapons that has a different nature from the use of force that is prohibited by international law,unless justified mainly as an exercise of the right of self-defense. These possibilities do, in reality,
exist.
Then, simply reflecting such possibilities in a theoretical framework would produce four
patterns of the use of weapons and the measures that the use of weapons accompanies: firstand second, when the nature of the measures is law enforcement, the use of weapons has either
the nature of the use of arms or the use of force; and third and fourth, when the nature of themeasures is self-defense,43 the use of weapons has either the nature of the use of arms or theuse of force. Such a framework may be called a theoretical framework based upon a case-bycase approach in the sense that there is no qualification with respect to the relationship between
the nature of the use of weapons and the nature of the measures that the use of weapons
accompanies. It admits no relationship between the nature of the measures, on the one hand, andthe nature of the use of weapons that accompanies them, on the other hand. Different from this, amore qualified approach is to set the presupposition that this author has proposed in her previous
work.
As a way to relate or not to relate the two issues to each other, logically speaking, there are
two possibilities. First, the nature of the measures decides the nature of the use of weapons,
and second, the nature of each issue is not related to the other. The second means a theoreticalframework based on a case-by-case approach, as explained here.44 It may not be reasonable to42

Regarding a case-by-case approach, see “Maritime Security,” 49–50.

43

In comparison to the expression “law enforcement,” it is difficult to find an established expression todescribe the nature of the measures that the use of force is likely to accompany. “Measures of selfdefense” is most likely presupposed. Another candidate is “measures for security.” However, as theconcept of maritime security has been expanding, “security” might cause confusion. Thus, without
excluding other possibilities, when it is appropriate, this article will use, to express the nature of suchmeasures, “measures for self-defense.”

44

There may be two different case-by-case approaches: the first type is under some defined framework forthe consideration of factors, and the second type is a simple one without any reference to a framework.
See “Maritime Security,” 49–50. When the “framework” is substantial, the first type comes close to thepresupposition that will be set forth below.

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think that the nature of the use of weapons decides the nature of the measures.45 This author,
by taking the first possibility, has proposed46 the presupposition that “in principle,” the nature of
the measures decides the nature of the use of force or arms in the measures. The qualification of“in principle” signifies that the consideration of the relevant factors in each case is not excluded
for deciding the nature of the use of force or the use of arms.47 In other words, by considering
the particular factors in individual cases, the nature of the measures and the nature of the useof weapons could be different from each other. With such a qualification, it is appropriate tomaintain this presupposition for the following reasons.
First, the case-by-case approach might cause chaos not only for the theoretical analysis, butalso for the actual operation at the scene. Theoretically, it would be solely descriptive, listing up
all possible patterns of the nature of the measures and that of the use of weapons, without any
analysis. Practically, it is almost impossible for the subjective entity exercising the use of weapons
to think through, on site, all possibilities for the nature of its use of weapons. The fundamental
purpose of the examination of this issue is above all to prevent violations of international law,which prohibits the use of force and regulates the use of weapons depending on its nature. Thus,
to provide a theoretical framework with some guidelines is appropriate and useful mainly forthe subjective entities exercising the use of weapons, rather than for providing a comprehensive
catalogue of the nature of the measures and the nature of the use of weapons.
Second, the presupposition can retain a level of flexibility with the qualification “in principle.”
This flexibility may replace, at least, to a certain degree, the significance that is expected for thecase-by-case approach. Therefore, while maintaining the aforementioned presupposition, next,
this article will examine various works on the meaning of the use of weapons.

3. Discussion of the “Force” under Article 2, Paragraph 4 of the UN Charter
While the issue of the distinction between the use of arms and the use of force has attracted
attention in relatively recent days, discussion of “force” has a longer history.48 Since the drafting

45

The subjective entity implementing the measures uses weapons provably with its own judgment thatthe use of weapons has the same nature as that of the measure, while such a subjective judgment is notnecessarily convincing nor objectively correct. On the contrary, apart from the nature of the measuresin which the use of weapons accompanies, the use of weapons itself does not bear the intent or judgment
as to its nature of the subjective entity who uses the weapons. Therefore, it is not reasonable to thinkthat the nature of the use of weapons may decide the nature of the measure that the use of weapons
accompanies. There may be a position that the nature of the use of weapons is determined based upon
its scale, but it might determine the nature of the use of weapons, not the nature of the measures.

46“Maritime Security,” 34–37.

47

Tom Ruys, “The Meaning of ʻForceʼ and the Boundaries of the Jus Ad Bellum: Are ʻMinimalʼ Uses ofForce Excluded from UN Charter Article 2(4)?,” American Journal of International Law, 108 (2014),
207.

48

Here the issue of the threat of force and that of economic coercion are not touched upon.

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process of the UN Charter, a significant number of works have been produced on this issue,49 andthe ICJ, in the 1986 Nicaragua Case (merits),50 declared an important definition of “armed attack,”
setting a substantial limitation on the exercise of the right of self-defense.51
In the works on this issue, generally speaking, there are two opposite opinions. One interprets
the prohibition of the use of force by Article 2, Paragraph 4 as all-inclusive. The other admits atype of use of weapons that the provision does not prohibit. It provides room mainly for the useof weapons at a small scale under the provision.52 In addition, it is said that in a State-to-State
context, even confrontation at a small scale comes within the ambit of the jus ad bellum. 53 An
interesting position from the perspective of this article is that Article 2, Paragraph 4, as an allinclusive provision, applies to the use of weapons at sea, even that accompanying law enforcementwith legal grounds.54
Here it is not necessar y to look into the detail of the discussion. The point is that there
is not a generally agreed opinion on the meaning of “force.” Furthermore, the reason for thedenial of the existence of the room mainly for the use of weapons at a small scale is to avoid theabuse of such room, and the lack of established international practice.55 This would seriously
deprive the prohibition, by international law, of the use of force of its significance. Therefore, as
49See, for instance, Ruys, op. cit., supra n. 47, 159–210; Tom Ruys and Sten Verhoeven, “Attacks by Private
Actors and the Right of Self-Defense,” Journal of Conflict & Security Law, 10 (2005), 193–206; Olivier
Corten, The Law against War: The Prohibition on the Use of Force in Contemporary International Law(Oxford: Hart Publishing, 2010); Rob McLaughlin, “Authorizations for Maritime Law Enforcement
Operations,” International Review of the Red Cross, 98 (2) (2016), 465–490; Koichi Morikawa, “Kokusai
Heiwakyoryoku Gaiko no Ichi Danmen―Kaijo Soshikodo he no Sanka/Kyoryoku wo Meguru Hoteki
Shomondai [An Aspect of Diplomacy for International Cooperation and International Peace― Legal
Issues with Respect to Participation in and Cooperation for Maritime Interdiction Operations],”
Nihongaiko to Kokusaikankei [Japanʼs Diplomacy and International Relations], (Naigai Shuppan, 2009),
243–282; by the same author, “Gurei Zon Jitai Taisho no Shatei to Sono Hoteki Seishitsu [Coping with
Grey Zones and Its Legal Implications],” Kokusai Mondai [International Affairs], 648 (2016), 29–38;
by the same author, “Kaijo Hoshikko ni Tomonau ʻUse of Forceʼ no Gainen [The Concept of the Useof Force in Conjunction with Law Enforcement],” in Kokusaiho no Dainamizumu [Dynamism inInternational Law], in Memory of Professor Akira Kotera, (Yuhikaku, 2019), 651–677; Kwast, op. cit.,
supra n. 4, 49–91.

50

Case Concerning Military and Paramilitary Activities in and against Nicaragua (Nicaragua v. UnitedStates of America), Judgment of 27 June 1986, ICJ Repor ts 1986 (hereinafter referred to as “theNicaragua Case (merits)”).

51

Ibid., para. 191.

52

Regarding these positions, see “Maritime Security,” 40 and the footnotes thereto. Corten, op. cit.,
supra, n. 49, 55 and 77. Other examples of the use of weapons that may be permitted under Article 2,
Paragraph 4 of the UN Charter, ibid., 55 and 85, 163–171. The position that there is room for the use offorce at a small scale under Article 2, Paragraph 4 of the UN Charter introduces the following examples:
the abduction of Mr. Eichmann from the territory of Argentina; violations of territorial airspace bymilitary aircraft; targeted killing of suspects of terrorism in the territory of a foreign country. Ruys, op.
cit., supra n. 47, 167–179.

53

Including other examples of the small scale of the use of weapons, Ruys, op. cit., supra n. 47, 171–187.
As examined above, Japan has been coping with Chinese government vessels and warships thatare periodically entering Japanʼs territorial sea surrounding the Senkaku Islands. As far as coercive
measures are necessary to effectively cope with the circumstance and actually taken by the JCG, thispoint has a critical meaning, as it is in the context of a State-to-State confrontation. This issue will beconsidered later in Section IV and Section V.

54

Douglas Guilfoyle, Shipping Interdiction and the Law of the Sea, (Cambridge University Press, 2009),
272–277: Morikawa, op. cit., supra n. 49 (Kaijo Hoshikko Katsudo), 659–661.

55

Ruys, op. cit., supra n. 47, 1, 163–171.

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far as effective law enforcement requires, on some occasions, the use of weapons,56 the criticalimportance resides in the prevention of the aforementioned abuse. For that purpose, the useof arms in law enforcement should be clearly defined so as to establish its legal justification
backed up by international practice.57 To achieve that goal, as in Section III, clarification of themeaning of law enforcement and identification of factors that reflect law enforcement become theindispensable starting point.
Before moving onto such an examination, some consideration of the issues regarding thepresupposition of the theoretical framework is useful. One is the issue related to the flexibility inthe distinction between the use of arms and the use of force. In particular, focus will be placed on
the impact of the wide understanding of maritime security on said flexibility. The other issue isthe legal effect of the distinction. Concretely speaking, this is the issue of the legal consequenceof the cases in which the actual use of weapons violates the relevant international law rules
regulating it. If the use of weapons in law enforcement breaches the international rules that
regulate them, would the nature of the use of weapons as “the use of arms in law enforcement”
change? These two issues will be dealt with in Section II in this order.

II. Issues Arising from the Theoretical Framework Thus Set For th for an
Examination of the Relationship between the Nature of the Measures and the
Nature of the Use of Weapons Accompanying Them
1. Flexibility in the Distinction between the Use of Arms and the Use of Force:
The Qualification “in Principle”
The presupposition of this article is that the nature of the measures, in principle, decides thenature of the use of weapons that accompanies them. The qualification “in principle” allows thispresupposition to be disproved in some cases.58 Generally speaking, individual cases should haveparticular circumstances and factors that should be considered when deciding the nature of themeasures and that of the use of weapons accompanying them.59 There might be examples inwhich the nature of the measures and the nature of the use of weapons are not identical, even if
only as exceptions.
In this regard, the wide understanding of maritime security likely has a significant impact.60
There has been a firm tendency to understand maritime security in a wide way, 61 whereby“maritime security is understood by the measures combatting not only traditional military threats,
but also terrorism, weapons proliferation, transnational crimes, piracy, environmental/resource
56

In the two cases introduced above, the court and the tribunal admitted the use of weapons in law
enforcement.

57

The main purpose of this article is to provide a way to identify the use of arms in law enforcement so
as to enable States to prove its use of weapons as such. At the same time, doing so enables, at least to acertain degree, the prevention of the abuse of weapons that eludes prohibition by Article 2, Paragraph 4of the UN Charter.

58

This does not necessarily entail admitting a case-by-case approach for the decision concerned. However,as mentioned above (supra n. 44), if a case-by-case approach is realized under some defined framework
for consideration of the relevant factors, it could not be denied that such a case-by-case approach would
come close to the presupposition of this article.

59

The factors are, for example, the scale of the violence on both the side of the wrongdoers and entities of
the use of weapons, the nature of the wrongdoers involved, the political intents of the wrongdoers, andthe legal interests being infringed upon by the violence of the wrongdoers. Ruys, op. cit., supra n. 47,
207.

60

“Maritime Security,” 50–51.

61

A typical example is Guilfoyle, op. cit., supra n. 5. As for other authorities, see supra n. 5.

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destruction, and illegal seaborne migration.”62 Another authority explains a unique reason for
the recent wide understanding of maritime security.63 According to this position, not only theexclusive interests of sovereign States but also the inclusive interests (common interests) of
the world define a wide array of threats such that maritime security is understood widely asthat combatting the variety of threats to these interests.64 As maritime security is acquiring awider meaning so as to include all measures for combatting such various incidents, self-defense
measures and law enforcement ones have inevitably come to be closely related to each other andeven intertwined.
In recent cases, as will be analyzed later, both ITLOS and the arbitral tribunal declared thatthe distinction between military measures65 and law enforcement measures has been blurred.66
This tendency likely also reflects the wide understanding of maritime security.
The tribunals made their decisions with respect to the nature of the measures and the use of
weapons accompanying them by considering those implementing the measures (navy or coast
guard, and militar y vessels or other government vessels), the characterization of the organs
involved (military or law enforcement organs), the series of facts constituting the context of theevent concerned, and the dominant factors in the aforementioned context.67 Such decisions areones based upon an objective evaluation.68 In the litigations, “objective” evaluation connotes anevaluation based upon facts and one that is made by the authoritative third parties independent of
the subjective evaluation by the parties to the disputes.
As the distinction between the natures of the measures, namely those for law enforcement
and those for self-defense, becomes flexible, so too does the distinction between the natures of
the use of weapons, namely those constituting the use of arms and those constituting the use offorce. This might be said to be the logical result of applying the presupposition that the nature of
the measures decides, in principle, the nature of the use of weapons. On the other side of a coin,
there could be a case in which even the qualification “in principle” would lose its significance,
and a definite relationship between the principle and an exception to it could not be identified.
If so, the nature of the measures and the nature of the use of weapons would be determined
independently, which means a case-by-case approach in deciding the nature of the measures and62

Guilfoyle, op. cit., supra n. 5, 299.

63

Klein, op. cit., supra n. 5, 1–10.

64

Ibid., 8.

65This article uses the term “measures for self-defense,” supra n. 43. The expression “military” usedhere is according to the parlance of ITLOS. That is also the parlance of UNCLOS, as its Article 298,
Paragraph 1 (b) contains the expression “military activities.”

66

Case Concerning the Detention of Three Ukrainian Naval Vessels (Ukraine v. Russian Federation),
Request for the Prescription of Provisional Measures, Order of 25 May, 2019, https://www.itlos.org/
fileadmini/itlos/documents/cases/26/published/C26_Order_2019025.pdf, (hereinafter referred
to as “the Detention Case”), para. 64. The arbitral tribunal, too, expressed a similar thought. In the
Matter of an Arbitration before an Arbitral Tribunal Constituted under Annex VII to the 1982 United
Nations Convention on the Law of the Sea, between Ukraine and the Russian Federation, in respectof the Dispute Concerning Coastal State Rights in the Black Sea, Sea of Azov and Kerch Strait, Award
Concerning the Preliminary Objections of the Russian Federation, 21 February 2020, https://pcacases.
com/web/sendAttach/9272, (hereinafter referred to as “the Coastal State Rights Case”), paras. 333–
335.

67

For a detailed examination of the cases, see Section, III 2.

68

For a detailed examination of the cases, see Section, III 2.

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Atsuko Kaneharathat of the use of weapons.69

2. Legal Consequences of Violations of the Legal Standards to Be Applied to the
Use of Arms and the Use of Force70
This article focuses upon the distinction between the use of arms and the use of force. It does
not deal with the legal standards regulating the use of arms or the use of force, nor the issue ofthe legal consequences of violations of these international legal standards.71 Solely in relation to
the unavoidable flexibility in the distinction mentioned here, and the furtherance of the flexibility
that is expected due to the continued expansion of the already wide understanding of maritime
security, the following remarks may be useful.
One authority suggests that in the case of violations of the international law rules that regulate
the use of arms or the use of force, the facts of the violations thereof do not impact on the natureof the use of arms or the use of force.72 This means that even if the use of arms in law enforcement
breaches the legal standards of unavoidability, reasonableness, and necessity, it would not bear,as a result of the violation, the nature of the use of force prohibited by international law. The legal
consequence of such violations is the incurrence of State responsibility for the reason of violatinginternational law, namely, international wrongful acts.73 In the same way, a case can be assumed
in which the use of force, as an exercise of the right of self-defense, violates internationalrules such as proportionality and necessity. However, it is unreasonable and unthinkable thatsuch a use of force would change into a use of arms that accompanies law enforcement. Thisis because the discussion here is conducted under the fundamental prohibition of the use offorce by international law. For admitting a legal use of weapons, room is sought for a use of
weapons in law enforcement with carefully preventing the abuse of the room. If the use of force,as the right of self-defense that violates the international regulation would change to the use ofarms in law enforcement, this would really cause an abuse of the room. Thus, the issue to be
assumed is whether the use of arms in law enforcement, if it breaches the rules that govern it,such as unavoidability, reasonableness, and necessity, becomes the use of force prohibited byinternational law.
The position that violations of the relevant international law rules would not bring about achange in the nature of the use of arms to that of the use of force would likely be approved if
it is based upon the presupposition of this article, namely, the presupposition that the natureof the measures, in principle, decides the nature of the use of weapons. According to said
presupposition, without special circumstances that justify an exception to the “principle,” thenature of the use of arms would not change, even when it breaches the legal regulations thatgovern it. Only in cases in which a violation of the relevant international law rules on the useof arms sets forth “special circumstances” to justify the “exception” would that ver y breachchange the nature of the use of arms from the use of arms in law enforcement to the use of force
prohibited by international law. However, it is not necessary to admit such a result, as from the69

This author has previously emphasized a “simple” case-by-case approach. This does not have any
referential legal frameworks under which the determination is given regarding the natures of themeasures and the use of weapons. In comparison, there could be a case-by-case approach that is
conducted under some defined reference framework, such as the relevant legal provisions that regulate
law enforcement measures and self-defense measures. See “Maritime Security,” 49–50. The difference
between the two case-by-case approaches might be a matter of the degree of flexibility in deciding thenatures of the measures and the use of weapons. See also supra n. 44.

70“Maritime Security,” 47–49.

71

As for this issue, see “Maritime Security,” 48–49.

72

Ruys, op. cit., supra n. 47, 202.

73

Articles on State Responsibility, Article 2.

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perspective of the remedy for injuries, the incurrence of State responsibility for the violation of
the international rules would suffice as the legal consequence of the violation of the relevantinternational law rules.
Rather, the necessity of such an exception to the “principle” according to which the use ofarms in law enforcement becomes the use of force prohibited by international law should be
examined with a consideration of the object and purpose of the strict position that the prohibitionof the use of force by Article 2, Paragraph 4 of the UN Charter is “all inclusive.”74 This position
denies the existence of any room for the use of weapons in order to prevent the abuse of suchroom.75 The importance of the prevention of such abuses could also be approved by the otherposition that the provision admits some use of weapons. Therefore, whether there do exist
special circumstances that form an exception to the “principle” and whether the use of arms inlaw enforcement changes to the use of force prohibited by international law should be decided inorder to avoid these abuses.
Beyond this general remark, it could be difficult to identify all concrete cases in which
violations of the international law rules would change the nature of the use of weapons fromthe use of arms in law enforcement to the use of force prohibited by international law. Rather, it
would be helpful to provide, as comprehensively as possible, the factors to be examined in orderto determine the use of arms in law enforcement. Under the clear tendency toward the wide
understanding of maritime security and, as its result, the increased flexibility in the distinction
between the use of arms and the use of force,76 clarification of those factors as comprehensively
as possible is strongly needed both for theories and practice. Thus, as the main part of thisarticle, Section III will conduct such an examination.

III. Identification and Proof of the Use of Arms in Law Enforcement
1. A n Attempt to Define the Use of Weapons That Is Not Prohibited or Is
Permitted by International Law as the Use of Arms Accompanying Law
Enforcement Measures

As examined above, it is not easy to identify the precise meaning of “force” that is prohibitedby international law. Authorities are not in accord in this regard.77 The serious concern of thoseauthorities taking the strict position that Article 2, Paragraph 4 of the UN Charter prohibits theuse of force in an all-inclusive manner is the abuse of the room that would otherwise be affordedby the provision. If one seriously considers this concern, it becomes necessar y to clarify asmuch as possible what the use of arms in law enforcement is, as it is indispensable for effective
law enforcement. In this regard, the use of weapons for effective law enforcement is commonly
admitted.78
Then, as a useful approach, by departing from the particular framework of arguments for theuse of force prohibited by international law, mainly Article 2, Paragraph 4 of the UN Charter, a
74

See Section I, 3.

75

Regarding the positions by the relevant authorities, see Section I.

76

In this regard, when the flexibility of the distinction between the use of arms and the use of force
significantly increases, such increased flexibility might require continuous reconsideration of the issue
discussed here.

77

See Section I, 3.

78

Strictly speaking, there may be dif ferences between the use of arms that is not prohibited byinternational law and the use of arms permitted by international law. With this reservation, hereinafter,such a phrase as “the use of arms that is permitted (allowed) by international law” will be used to meanboth, if there is not expected to be any confusion.

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new line of argument may arise. A reasonable way to define the use of weapons is by looking forthe definition or justification thereof. In addition to the relevant international laws with respect
to law enforcement measures to be taken at sea, various candidates will be taken up as many as
possible.79 This is the way to determine, in a “positive” manner, the nature of the use of weapons
accompanying the law enforcement measures taken at sea based upon the relevant internationallaw. It is different from the determination, in a “negative” manner, of such use of weapons as thatis not prohibited by international law.
The presupposition of this paper is that the nature of the measures, in principle, decides thenature of the use of weapons. Therefore, to identify the nature of the use of arms accompanying
law enforcement measures as law enforcement, it is necessary to determine that the measures forwhich the arms are used are those of a law enforcement nature. As the qualification “in principle”
indicates, there are exceptions to the “principle” that the nature of the measures decides thenature of the use of weapons. Two logical possibilities are: first, while the nature of the measuresis law enforcement, the use of weapons accompanying them has the nature of the use of force;second, while the nature of the measures is self-defense, the use of weapons has the nature of theuse of arms in law enforcement. It is so difficult to determine in an abstract way such exceptions
as causing the difference between the nature of the measures and the nature of the use of
weapons accompanying them. Accordingly, it is not possible to provide a complete analysis ofevery pattern of the use of weapons under that presupposition of this article.
In place of such a complete analysis, the following part of this Section will rather conduct thethorough examination of the use of arms in law enforcement. Considering the prohibition of theuse of the force by the fundamental international law, and as far as the use of weapons should beallowed for effective law enforcement, as the room that escapes from the prohibition, preventionof any abuse of the room is critical. By providing the solid understanding of the use of arms
with rich proof thereof, the thorough examination of the use of arms should contribute to themaintenance of the fundamental restriction of the force of international law.
Several authorities and the jurisprudence have discussed the definition of “law enforcement.”80
Nonetheless, a precise definition has not been firmly established. Therefore, it is helpful toconsult the relevant provisions of UNCLOS that are interpreted as both overtly and covertly
dealing with law enforcement.81 This author has already conducted such an examination82 andwill not repeat this here. It can be safely said that the provisions of UNCLOS and customary
79

This is the method that this author has taken in her previous work, “Maritime Security,” 43–44.

80See, for instance, Rekizo Murakami and Masato Mori, “Kaijo Hoancho Ho no Seiritsu to Gaikoku Hoseino Keiju―Kosutogado Ron [The Establishment of Japanʼs Coast Guard Law and Succession of Foreign
Laws―Coast Guard―],” in Soji Yamamoto ed., Kaijo Hoan Hosei–Kaiyo Ho to Kokunai Ho no Kosaku[Laws on Coast Guard―Interplay between the Law of the Sea and Domestic Law], (Sanseido, 2009), 30–
31; see also infra n. 83; Kwast op. cit., supra n. 4, 53–57. Regarding the relationship between maritime
law enforcement and other related concepts, see Craig H. Allen, “Limits on the Use of Force in Maritime
Operations in Support of WMD Counter-Proliferation Initiatives,” International Law Studies, 81 (2006),
77 et seq.; Nils Melzer and Gloria Gaggioli Gasteyger, “Conceptual Distinction and Overlaps between
Law Enforcement and the Conduct of Hostilities,” in Terry D. Gill and Dieter Fleck eds., The Handbookof the International Law of Military Operations, 2nd ed., (Oxford University Press, 2015), Chapter 4.

81

That is not to mention that many provisions under UNCLOS regarding law enforcement succeeded
those of the four 1958 Geneva Conventions on the Law of the Sea, and they may have the status ofcustomary international law. It has been pointed out that due to the sensitive nature of the mattersconcerned, except for Article 73 on exclusive economic zones, UNCLOS has provisions that merely
assume or imply law enforcement with respect to territorial seas, archipelagic waters and contiguous
zones; see Ivan Shearer, “The Development of International Law with Respect to the Law Enforcement
Roles of Navies and Coast Guards in Peacetime, International Law Studies, 71 (1998), 435.

82

“Maritime Security,” 44–45.

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international law rules provide for the rights and therefore also the justification to take law
enforcement measures.83 The point is that the relevant international law rules on law enforcement
set forth the strong evidence that measures taken in accordance with them have the nature oflaw enforcement.84 In the remaining part of this Section, after a succinct analysis of the recent
jurisprudence, other factors to be considered in order to determine the nature of the measures
will be proposed.

2. Recent Jurisprudence Regarding the Distinction between Law Enforcement
Measures and Militar y Measures(1)Traditional and Preceding Jurisprudence
In terms of traditional cases that can be interpreted as touching upon the issue of the use of
weapons in the context of law enforcement, there are the Iʼm Alone Case,85 the Red Crusader
Case,86 the Fisheries Jurisdiction Case,87 the Saiga Case,88 and the Guyana and Suriname Case.89
This author has already examined some of them elsewhere,90 and this article introduced therelevant parts of the Fisheries Jurisdiction Case and the Saiga Case above.91 Therefore, here, it
may suffice to solely provide some complementary remarks.
Based upon the jurisprudence, the authorities are mostly in accord that the rules on the useof weapons in law enforcement92 are those of “unavoidability,” “proportionality,”93 and “necessity.”94
The ICJ admits the use of weapons in law enforcement in the Fisheries Jurisdiction Case. It reads:(I)f the officer “believes on reasonable grounds that the force is necessary for the purpose ofarresting” the master or crew (Section 8.1). Such provisions are of a character and type to be83

After careful consideration of the possible categorization of law enforcement and similar measures thathave been indicated by several authorities, Morikawa, bearing in mind the enforcement jurisdictionof States under the law of the sea, concluded that for the purpose of the examination of the use of
weapons, a wide understanding of law enforcement is appropriate. Morikawa, op. cit., supra n. 49 (Kaijo
Hoshikko), 655–659.

84

As for a general review of UNCLOS in relation to its authorizations of law enforcement measures, see
McLaughlin, op. cit., supra n. 49, 465–490.

85

The Iʼm Alone Case, Report of International Arbitral Awards, 3 (1935), 1609. For a detailed analysis of
this case, see Gerald. G. Fitzmaurice, “The case of the Iʼm Alone,” British Year Book of InternationalLaw, 17 (1936), 82–111.

86

The Red Crusader Case, International Law Reports, 35 (1962), 499.

87

Supra n. 34.

88

Supra n. 35.

89

In the Matter of an Arbitration between Guyana and Suriname in the Award of 17 September 2007,https://pcacases.come/web/sendattach/902/.

90“Maritime Security,” 41–43.

91

See Section I, 1.

92

Precisely speaking, none of the cases clearly define the circumstance as that of law enforcement before
the court and tribunals. Nevertheless, it is useful, here, to confirm the rules that can be derived fromthe decisions and judgments.

93

One authority opines that no use of weapons (according to him, the expression is “force”) beyond
proportionality could ever be one of last resort. Guilfoyle, op. cit., supra n. 54, 280–281.

94

Regarding the arbitral decision in the Iʼm Alone Case, it is said that intentional bombardment andsinking are not allowed in cases of usual crimes, and that this would become the use of force as selfdefense, not law enforcement. Here, the scale and/or intent of the bombardment and sinking may befactors that could change the nature of the use of weapons from that of law enforcement to that of selfdefense.

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found in legislation of various nations dealing with fisheries conservation and management, as
well as in Article 22 (1) (f) of the United Nations Agreement on Straddling Stocks of 1995.95
The ICJ confirmed the practice of not only domestic laws but also the UN Agreement on
Straddling Stocks, Article 22, Paragraph 1 whereby the use of weapons (according to the ICJ, theexpression is “force”) is allowed if it is necessary for the purpose of arrest based upon reasonablegrounds.
This evaluation by the authorities of the jurisprudence reflects their recognition of the law
enforcement measures and the category of the use of arms in law enforcement, while all the court
and tribunals did not necessarily determine it.
The circumstances in which weapons were used were different in each case. In this regard,
the Guyana and Suriname Case is of interest. In this case, while it is not crystal clear, the arbitral
tribunal seems to define the military action as being wider than law enforcement, and so theformer includes the latter.96 This seems to be similar to the interpretation of Article 2, Paragraph
4 of the UN Charter that the prohibition of the use of force is all-inclusive, as far as both do not
admit a special category of the use of weapons for the purpose of law enforcement. Here, it isenough to confirm that the arbitral tribunal and the ICJ permit the use of weapons for the purposeof law enforcement, under certain conditions.
(2)Recent Jurisprudence① The Ukraine Naval Vessels Detention Case (Provisional Measures and Preliminary Objections)
In the Detention Case,97 the interpretation of “military activities” in Article 298, Paragraph 1 (b)of UNCLOS was discussed.98 The crux of the discussion is centered on whether the disputeconcerns military activities or not. If the answer is yes, ITLOS cannot have jurisdiction over it.99
After its confirmation of the positions of the parties,100 ITLOS rendered its decision, the gist ofwhich is as follows.
First, the entity engaging in the acts, whether military vessels or law enforcement vessels,
does not decide the nature of the measures, although this is a factor to be considered. The
traditional distinction between naval vessels and law enforcement vessels in terms of their95

Supra n. 34, para. 81.

96

Guilfoyle, op. cit., supra n. 54, 275.

97

Supra n. 66.

98

Article 298, Paragraph 1 (b) reads:
disputes concerning military activities, including military activities by government vessels andaircraft engaged in non-commercial service, and disputes concerning law enforcement activities inregard to the exercise of sovereign rights or jurisdiction excluded from the jurisdiction of a court or
tribunal under article 297, paragraph 2 or 3;
The key part is the expression “sovereign rights or jurisdiction.” Precisely speaking, these terms do not
apply to territorial seas, as the coastal States of territorial seas have sovereignty, not “sovereign rights”
or “jurisdiction.” As a logical conclusion, this exception under Article 298, Paragraph 1 (b) does not
apply to any activities taking place in territorial seas. See F. David Froman, “Uncharted Waters: Noninnocent Passage of Warships in the Territorial Sea,” San Diego Law Review, 21 (1984), 671–672. In thejurisprudence, maybe due to the special circumstance regarding Crimea, the tribunals did not touchupon this issue.

99

Supra n. 66, para. 50.

100

Ibid., paras. 51–53 (Russia), paras. 54–62 (Ukraine).

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roles has become considerably blurred.101 Second, the distinction between militar y and law
enforcement activities must be based primarily on an objective evaluation of the nature of
the activities in question, taking into account the relevant circumstances in each case. 102
Such an “objective ” evaluation is in contrast to the “subjective ” claim by the parties to thedispute.103 Therefore, it is understood that “objective” may have two significances: an objective
evaluation should be based upon the facts; and the evaluation should be conducted by neutral
and authoritative third parties, which means the tribunal. Third, the series of events need to
be examined, and consideration is necessar y as to whether the specific acts such as arrestand detention in the case concerned took place in the context of a military operation or a law
enforcement operation.104 The context may consist of a series of events, and the usage, by thetribunal, of “context” is similar to this authorʼs usage of “situations,” as explained above.105
In addition, the tribunal considered the particular circumstances of the case concerned: thepassage of the Ukrainian naval vessels through the Kerch Strait;106 the core of the dispute was thepartiesʼ differing interpretation of the regime of passage through the Kerch Strait;107 the force108
was used by the Russian federation in the process of arrest, and the context of the use of force
has particular relevance.109
As its conclusion, the tribunal decided that the sequence of events constituted the context of alaw enforcement operation rather than a military operation, and that Article 298, Paragraph 1 (b)of UNCLOS does not apply.110
Thus, the tribunal determined the nature of the use of weapons by Russia by considering
the sequence of events or the context, which is, according to this author, the situation. By thisauthorʼs terminology, the nature of situations is the same as the nature of measures. The tribunalʼsterminology of the “context” seems to be the same as this authorʼs terminology of the “situations.”
The tribunal does not clarify the following two issues: the issue of the nature of the measures andthat of the nature of the use of weapons. Nonetheless, the tribunalʼs position is the same as that101

Ibid., para. 64. The same position is heard by authorities such as David H. Anderson; see “Some Aspectsof the Use of Force in Maritime Law Enforcement,” in Nerina Boschiero, Tullio Scovazzi, Cesare Pitea,
and Chiara Ragni eds., International Courts and the Development of International Law―Essays in
Honour of Tullio Treves, (Springer, 2012), 141. It has even been pointed out that the distinction between
warships and merchant vessels has been called into question, see Vaughan Lowe, “Ships,” in ibid., 297.
Furthermore, to cope with piracy, for the purpose of vessel protection, armed military personnel are on
board merchant vessels; see Valeria Eboli and Jean Paul Pierini, “Coastal State Jurisdiction over Vessel
Protection Detachments and Immunity Issues: The Enrica Lexie case,” Military Law and Law of War
Review, 51 (1) (2012), 118–122. See also Wolff Heintschel von Heinegg, “The Difficulties of Conflict
Classification at Sea: Distinguishing Incidents at Sea from Hostilities,” International Review of the Red
Cross 98 (2) (2016), 449–453.

102

Supra n. 66, para. 66.

103

Ibid., para. 65.

104

Ibid., para. 67.

105

For the terminology used in this article, see the Introduction, 1.

106Supra n. 66, para. 68. According to the tribunal, it is difficult to state that the passage of naval ships per
se amounts to a military activity.

107

Ibid., paras. 71–72.

108

The tribunal uses the term “force.” Here it means the physical use of weapons according to theterminology of this author.

109

Supra n. 66, para. 73.

110

Ibid., paras. 74–75. In addition, the tribunal mentioned that the subsequent proceedings and charges
against the servicemen further support the law enforcement nature of the activities of Russia. Ibid.,para. 76.

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Atsuko Kaneharaof this author, in that the nature of the measures, in principle, decides the nature of the use of
weapons, if the tribunal admits the possibility that the nature of the context and the nature of theuse of weapons may be different depending on the individual factors of each case, although thiswould be exceptional. At least in some sense, the tribunalʼs thorough consideration of the three
special factors111 to the dispute might endorse such a possibility. Such thorough consideration of
inherent factors to the case concerned might bring about the conclusion that the nature of themeasures in the given context and the nature of the use of weapons are different from each other.
Regarding the later decision by the tribunal at the preliminary objections stage of this case,112
the following points deser ve attention. First, the tribunal emphasized the importance of therelevant circumstances in each case for the objective evaluation of the nature of the activities
concerned.113 Different from Ukraineʼs position,114 the tribunal denied the “either-or” proposition
regarding the distinction between military activities and law enforcement ones. According to thetribunal, activities that initially have a law enforcement character may become activities with amilitary character, and vice versa.115 After thorough consideration of the material facts, which thetribunal divided into three phases, regarding the second phase, it left its decision as to whether or
not there were military activities to the merits stage.116② The Coastal State Rights Case (Preliminary Objections)
The same parties opposed each other in an arbitration case, the Coastal State Rights Case(preliminary objections).117 In this case, too, “military activities” under Article 298, Paragraph 1 (b)were discussed. The gist of the decision is as follows.
First, the tribunal did not place weight on the entity that engaged in the activities of concern.
It said that military activities need not necessarily be carried out by military vessels and aircraft,
but can, instead, equally be performed by “government vessels and aircraft engaged in noncommercial ser vice.”118 Second, while it is a factor to be considered, the mere involvement
or presence of a military vessel is not sufficient to trigger the military activities exception of
Article 298, Paragraph 1 (b).119 The tribunal said that this is the meaning of Paragraph 1158 of
the decision rendered by the arbitral tribunal on the South China Sea Dispute (merits).120 Third,
there is no consistent State practice as to the scope of activities to be regarded as being exercised111

Ibid., paras.68–75.

112

In the Matter of an Arbitration before an Arbitral Tribunal Constituted under Annex VII to the 1982
United Nations Convention on the Law of the Sea, between Ukraine and the Russian Federation, in
respect of a Dispute Concerning the Detention of Ukrainian Naval Vessels and Servicemen, Awardon the Preliminary Objections of the Russian Federation, 27 June, 2022, https://pcacases.com/web/
sendAttach/38096.

113

Ibid., para. 109.

114

Ibid., para. 89.

115

Ibid., para. 121.

116

Ibid., para. 125.

117

Supra n. 66.

118

Ibid., para. 333.

119

Ibid., para. 334.

120

In the Matter of the South China Sea Arbitration, an Arbitral Tribunal Constituted under Annex VII to
the 1982 United Nations Convention on the Law of the Sea between the Republic of the Philippines andthe Peopleʼs Republic of China, Award of 12 July, 2016, https://pcacases.com/web/sendAttach/2086,(hereinafter referred to as “the South China Sea Dispute”). This paragraph was invoked by Russia,
supra n. 66, para. 308.

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Reconsideration of the Distinction between the Use of Arms in Law Enforcement
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by “military” vessels, aircrafts, and personnel.121 Use of “physical force” is not enough to conclude
that an activity is military in nature. The broader context in which the alleged event took placeshould be considered.122 Fourth, the mere involvement of military vessels or personnel in an
activity does not ipso facto render the activity military in nature.123
These points almost echo those determined by ITLOS in the Detention Case. In addition, thefollowing point deserves attention. The tribunal said that law enforcement forces, for example,
are generally authorized to use physical force without their activities being considered military
for that reason.124 The tribunal clearly admits the use of weapons in law enforcement. While it is
not entirely clear, the position of the tribunal seems to be different from that taken by the tribunal
in the Guyana and Suriname Case. As confirmed above, in the latter, the tribunal seems to define
military action as being wider than law enforcement, and so the former includes the latter. This
seems to be similar to the interpretation of Article 2, Paragraph 4 of the UN Charter that theprohibition of the use of force is all-inclusive, as far as both do not admit a special category of
the use of weapons for the purpose of law enforcement.125 Separately, while some uncertainty
remains, the tribunal in the Coastal State Rights Case instead admits a different category of theuse of weapons from the use of force under Article 2, Paragraph 4 of the UN Charter, and the useof weapons in law enforcement and the use of force prohibited by international law form different
categories from each other.
In the Coastal State Rights Case, the tribunal considered the “law enforcement activities”
exception under Article 298, Paragraph 1 (b) of UNCLOS.126 By taking the position that the status
and the sovereign rights should be established beforehand for the purpose of the applicationof the “law enforcement activities” exception, the tribunal rejected Russiaʼs objection.127 This isbecause the sovereignty over Crimea and the status of the sea area concerned as an exclusive
economic zone cannot be determined.128
Two points should be well considered before deriving general conclusions from thejurisprudence. First, the examination of Article 298, Paragraph 1 (b) of UNCLOS above all
relates to the issue of judicial and arbitral jurisdiction.129 Therefore, for instance, the issue of theinterpretation of “concerning” not “arising from” in the provision does not have a direct relation to121

Supra n. 66, para. 335.

122

Ibid., para. 336. The tribunal considered the broader context in which the alleged event took place,and determined that the use of physical force alleged by Ukraine does not turn the dispute into one
concerning military activities.

123

Ibid., para. 340.

124

Ibid, para. 336.

125

Supra n. 54.

126

Supra n. 66, paras. 353–358.

127

In this regard, Ukraine states that when a State is alleged to have violated UNCLOS in respect ofanother Stateʼs exclusive economic zone, the “law enforcement exception” does not apply; ibid., para.
349. It relies on the rulings on the South China Sea Dispute and the Arctic Sunrise Arbitration (TheNetherlands v. The Russian Federation). Infra n. 138.

128

Supra n. 66, paras. 356–358.

129

It is interesting to consider what the impact of the CCGL is, which placed Chinese coast guard vessels
under military control. Are the activities by Chinese coast guard vessels easily admitted as “militaryactivities” under Article 298, Paragraph 1 (b) of UNCLOS? In this regard, one authority points out that
the CCGL makes it difficult for rival claimants to overcome Chinaʼs militar y activities exception in
respect of future UNCLOS dispute settlement proceedings; see Alex P. Dela Cruz, “Marching towards
Exception: The Chinese Coast Guard Law and the Military Activities Exception Clause of the Law of the
Sea Convention,” The Journal of Territorial and Maritime Studies, SUMMER/FALL 2021, Vol. 8, 5 and
17.

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the issues that this article is examining. Second, from a broader perspective, in the backgroundof the jurisprudence, there is more or less motivation of either widening or reducing judicial or
arbitral jurisdiction. Third, that is not to mention that each case has its own inherent facts.
With serious reser vation on these points, par ticularly from the analysis of the recent
jurisprudence, nonetheless, we can derive useful guidance to treat the issues that this article isexamining.
From the jurisprudence, it can be safely said that the tribunals recognize the use of weapons
for the purpose of law enforcement. It is not clear whether such use of weapons forms an
exception to the prohibition of the use of force under Article 2, Paragraph 4 of the UN Charterwith the same rule of customary international law. The use of arms in law enforcement may set
forth a different and sort of parallel category to the category of the use of force that comes under
Article 2, Paragraph 4 of the UN Charter with the same customar y international law. In thisregard, some differences can be found between the explanation by the tribunal in the Guyana
and Suriname Case and that by the tribunal in the Coastal State Rights Case. For the definite
establishment of the use of arms in law enforcement, it would be more appropriate to admit aninherent category of the use of arms in law enforcement and to refine the international regulation
thereon.130
The jurisprudence makes the distinction between the use of weapons in law enforcement andthat in a military act. Nonetheless, it is not certain whether the tribunals understand this as two
issues: the nature of the measures, and the nature of the use of weapons. Regarding the possibilityof the difference between the nature of the measures and the nature of the use of weapons, isthere a use of weapons accompanying law enforcement measures that is characterized as the useof force that Article 2, Paragraph 4 assumes? Vice versa, is there a use of weapons accompanying
self-defense measures that is characterized as the use of arms in law enforcement?
This article sets the presupposition that the nature of the measures, in principle, decides thenature of the use of weapons. In what case would the qualification “in principle” be applied so as
to admit an exception to the presupposition? It is difficult to answer this question in an abstract
way. In individual cases, some factors might justify the exception. The jurisprudence declared
the existence of flexibility in the distinction between law enforcement activities and militar y
activities.131 In addition, the tribunals took a position of conducting thorough consideration of thematerial facts, particularly in the Detention Case. In its preliminary objection stage, the tribunal
even left its decision as to whether or not there were military activities to the merits finding.
Considering these stances of the tribunals, they might admit the potential for the occurrenceof a dif ference between the nature of the measures and the nature of the use of weapons
accompanying them, depending on the individual factors in each case.
With respect to “military activities,” whereas the tribunals have a tendency to take a restrictive
position on admitting the “military activities exception” under Article 298, Paragraph 1 (b) of
UNCLOS, in contrast to this, there is a position of defining military vessels widely.132 According
to this position, the existence of militar y vessels is admitted even if they are not militarily
equipped, not conducting military activities,133 nor even carrying members of the navy or marines

130

This is the “positive” position that this author has taken in examining the legal status of the use of
weapons for the purpose of law enforcement. See “Maritime Security,” 43–44.

131

See the analysis of the two cases above.

132

Article 29 of UNCLOS provides for a definition of military vessels.

133

This position is suggested by Lori Fisler Damrosch, “Military Activities in the UNCLOS Compulsory
Dispute Settlement System: Implications of the South China Sea Arbitration for U.S. Ratification of
UNCLOS,” AJIL Unbound, 110 (2016), 275.

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Reconsideration of the Distinction between the Use of Arms in Law Enforcement
and the Use of Force Prohibited by International Law—With an Analysis of the Inherent Significance of This Issue to Japan—

on board.134 As far as the jurisprudence examined above considers the entity implementing
the measures and the use of weapons accompanying them, the wide understanding of military
vessels may have some impact on the determination of “military activities.” Such a wide definitionof military vessels may relate to the interpretation of “non-innocent” passage of foreign vessels interritorial seas by this kind of vessels.135 Here, it suffices solely to point this out.
Thus far, from the jurisprudence, some guidance has been derived to make the distinction
between the use of arms in law enforcement and the use of force prohibited by international law
unless justified mainly as self-defense. Based upon the above examination, the next part of thisSection will look for possible tools to prove the nature of the use of arms in law enforcement.
There are various tools for this, such as rules, rights, factors, and so on. A certain categorization
will be provided, albeit a tentative one.

3. Possible Tools for Proving the Nature of the Use of Arms in Law Enforcement(1) Provisions on Law Enforcement under UNCLOS and Other Relevant Treaties
As explained above, this author has examined the relevant provisions of mainly UNCLOS andthe relevant treaties on law enforcement at sea elsewhere.136 In addition to said examination, thefollowing complementary consideration deserves attention.
First, UNCLOS and other treaties do not always have adequate provisions on law enforcement.
Some provisions implicitly designate law enforcement, such as Article 2, Article 25, and Article
111 of UNCLOS. In addition, while Article 73 prescribes law enforcement on the conservationand management of living resources,137 regarding structures138 and marine scientific research in
exclusive economic zones, UNCLOS does not clearly provide for law enforcement. Consideringsuch facts, it is critical to precisely interpret all provisions that possibly set forth justification
for law enforcement. Second, international law has not firmly established the definition oflaw enforcement, and similar activities may have the same function as law enforcement. One
example is Article 21, Paragraph 1 of the 1995 Fisheries Stock Agreement, which provides formeasures similar to but different from those of law enforcement at sea.139 Third, even the various
authoritiesʼ opinions are not in accord in relation to rights or right holders of law enforcementin cases of, for example, marine scientific research140 and any uses of oceans in the disputed sea

134

Bernard H. Oxman, “The Regime of Warships under the United Nations Convention on the Law of theSea,” Virginia Journal of International Law, 24 (1984), 813.

135

See Article 19 of UNCLOS. In particular, Paragraph 1 may be interpreted as meaning that “noninnocence” is established based upon the kind of foreign vessels in question.

136“Maritime Security,” 44–46.

137

Coastal States of exclusive economic zones have jurisdiction on the protection and preservation of themarine environment, and Part XII of UNCLOS provides for precisely the distribution of the jurisdictionof law enforcement depending on sources of pollution and the sea areas where pollution occurs.

138

In this regard, while Russia took law enforcement measures against the foreign vessel in the safety zone,
the tribunal in the Arctic Sunrise Case (merits) did not take up the issue of the right of law enforcementwith respect to structures of coastal States of exclusive economic zones; see In the Matter of the Arctic
Sunrise Arbitration before an Arbitral Tribunal Constituted under Annex VII to the 1982 United Nations
Convention on the Law of the Sea (The Kingdom of the Netherlands and The Russian Federation)Award on Merits, 14 August 2015, paras. 242 et seq., https://pcacases.com/web/sendAttach/1438.

139

Morikawa, op. cit., supra n. 49 (Kaijo Hoshikko), 657.

140

Alfred H. A. Soons, “Law Enforcement in the Ocean̶An Overview,” WMU Journal of Maritime Affairs,
3 (2004), 5.

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areas.141 Therefore, in the following examination, a broad and thorough search of the possible
tools is surely the most appropriate way of finding proof of the use of arms in law enforcement.142(2) The Legal Nature of the Sea Areas Concerned and Rights in Relation Thereto
Several authorities have opined that the legal nature of the sea areas concerned and the coastal
Stateʼs rights may provide, at least, the factors to be considered in order to prove that the natureof the measures and the use of arms accompanying them are law enforcement.143 In addition to
the provisions of UNCLOS and other treaties144 that expressly and implicitly admit the right totake law enforcement measures to coastal States, sovereignty over territorial seas,145 sovereign
rights and jurisdiction over exclusive economic zones146 may form the ground for law enforcementby coastal States.147 In this regard, the difference of the object and purpose of these rights and thelegal status of the sea areas should be carefully considered.
Coastal States exercise sovereignty over territorial seas and internal waters to protect theirpeace, good order and security.148 By contrast, coastal States of exclusive economic zones exercise
sovereign rights and jurisdiction. Exclusive economic zones are not high seas nor territorialseas, either.149 When Article 25 and Article 30 regarding territorial seas apply mutatis mutandis to
exclusive economic zones, depending on the territorial sea or exclusive economic zone, different
considerations are needed regarding the relationship between the rights of the coastal States, on
the one hand, and the right of navigation of foreign vessels150 and the immunity that they enjoy,151
141

Ibid. That is not to mention that Article 74, Paragraph 3 and Article 83, Paragraph 3 provide for the
obligations of the State concerned with respect to maritime delimitation for exclusive economic zones
and the continental shelf. However, these provisions do not make clear which of the States concerned
has the right of law enforcement on which use of oceans and the seabed, and to which States the State
concerned owes the obligations: the other party to the dispute on delimitation, third States, or both.
See Atsuko Kanehara, “Marine Scientific Research Conducted in Disputed Sea Areas Including Seabed
Where Delimitation Is Not Agreed̶An Analysis from General and Particular Perspectives of the East
China Sea,” in Keyuan Zou and Anastasia Telesetsky eds., Marine Scientific Research, New Marine
Technologies and the Law of the Sea, (Brill/Nijhoff, 2021), 206–223.

142

Regarding the competence of law enforcement, a special case is the Iʼm Alone Case. In this case, it was
the license or faculty to take measures provided for by the Convention concluded between the U.S. andthe UK; see Fitzmaurice, op. cit., supra n. 85, 96.

143

Mainly in relation to exclusive economic zones; Rob McLaughlin, “Coastal State Use of Force in theEEZ under the Law of the Sea Convention 1982,” University of Tasmania Law Review, (1999), 13–19.

144

Certainly, customary international law rules should never be excluded.

145

While UNCLOS does not have explicit provisions on this, there is no argument that coastal States havesovereignty over internal waters.

146

In reality, law enforcement on the continental shelf is, from a physical standpoint, difficult to assume.

147

McLaughlin, op. cit., supra n. 143, 13–19.

148

Regarding territorial seas, Article 19, Paragraph 1 of UNCLOS clearly provides for them.

149

Rüdiger Wolfrum “Restricting the Use of the Sea to Peaceful Purposes: Demilitarization in Being?,”German Yearbook of International Law, 24 (1981), 237; A. V. Lowe, “Some Legal Problems Arising fromthe Use of the Seas for Military Purposes,” Marine Policy, 10 (3) (1986), 178.

150

For territorial seas, it is the right of innocent passage, and for exclusive economic zones, it is the
freedom of navigation. On the high seas and in exclusive economic zones, regarding the legal interestson the side of the vessels targeted by the law enforcement, stateless ships would raise particularissues. See Allyson Bennett, “That Sinking Feeling: Stateless Ships, Universal Jurisdiction, and theDrug Trafficking Vessel Interdiction Act,” Yale Journal of International Law, 37 (2) (2012), 433–462;
Ted L. McDorman, “Stateless Fishing Vessels, International Law and the U.N. High Seas Fisheries
Conference,” Journal of Maritime Law and Commerce, 25 (4) (1994), 531–556.

151

Lowe, op. cit., supra n. 149, 180–181.

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on the other hand.
Coastal States of exclusive economic zones exercise their sovereign rights and jurisdiction
for their own interests and/or the common interests of international society. For instance,
while coastal States of exclusive economic zones have jurisdiction over marine environmental
protection, such protection is not only in the interest of the coastal State but also that ofinternational society. With respect to the sovereign right over the fishery resources of exclusive
economic zones, ITLOS implicated that it should be exercised for the common interest ofinternational society in its advisory opinion on the request for an advisory opinion submitted by
the SRFC.152 The following points reflect such a position by ITLOS. ITLOS emphasizes not thesovereign “right” of coastal States for the purpose of exploring and exploiting, conserving andmanaging the natural resources, but their responsibility for it.153 Furthermore, it declared that theconservation and management of fishery resources form part of the marine environment.154
These examinations are based upon the ocean zone system under the law of the sea that
forms the legal bases of the rights and jurisdictions of coastal States. There are even cases thatdepart from the ocean zone system.
First, when law enforcement is internationally authorized by, for instance, the resolutions of
the UN Security Council, the “law” may become international law, rather than the domestic lawsof the States taking the enforcement measures concerned.155 With international authorization,even in foreign territorial seas where such law enforcement is conducted, the legal status of theterritorial seas will change to international sea areas rather than the territorial seas of coastal
States.156 Second, when the coastal States of internal waters are allowed to take enforcement
measures against foreign vessels beyond internal waters, their justification would not consist of
the legal status of sea areas based upon the ocean zone system.157 In addition, law enforcement
according to Article 111 of UNCLOS in the high seas and foreign exclusive economic zones is an
exercise of the right of the coastal State of a territorial sea, contiguous zone, exclusive economic
zone, and continental shelf, depending on the place where the violations of the domestic lawsof the coastal State occur. The pursuit regime itself depar ts from the ocean zone system.
Third, in respect to the same right of coastal States and the rights of coastal States on the same
matter (ocean use), the legal interests to be protected by these rights are various. For instance,
regarding submarine cables and pipelines, the relevant interests may be natural resources and/or security.158 Thus, when justifying the law enforcement by coastal States, the rights of coastal
States may form the justification, but, in addition to that, the legal interests to be protected by thelaw enforcement may further substantiate the justification.
As to the legal interests of coastal States, when the security of coastal States is concerned, this152

Request for an Advisor y Opinion Submitted by the Sub-Regional Fisheries Commission (SRFC)
Advisory Opinion of 2 April 2015, https://www.itlos.org/fileadmin/itlos/documents/cases/case_no.21/
advisory_opinion_published/2015_21-adop.E.pdf.

153

Ibid., para. 104.

154

Ibid., para. 120.

155

McLaughlin, op. cit., supra n. 49, 481.

156

Regarding this issue, see, for instance, Rob McLaughlin, “United Nations Mandated Naval Interdiction
Operations in the Territorial Sea?” International and Comparative Law Quarterly, 51 (2002, April),
264–267; by the same author, “The Continuing Conundrum of the Somali Territorial Sea and Exclusive
Economic Zone,” International Journal of Marine and Coastal Law, 30 (2015), 305 et seq.; Martin D.
Fink, “UN-Mandated Maritime Arms Embargo Operations in Operation Unified Protector,” Military Law
and The Law of War Review, 50 (2011), 245–258.

157

Regarding the cases of internationally authorized operations, see, for instance, ibid., 248–249.

158

As a similar consideration, see Lowe, op. cit., supra n. 149, 179–180.

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Atsuko Kanehararaises the issue of the relationship between the right of self-defense under Article 51 of the UN
Charter and general international law, on the one hand, and the right of coastal States under thelaw of the sea, on the other hand. This will be examined later, particularly in relation to coastal
Statesʼ measures against foreign vessels that enjoy immunity.159(3) Factors to Be Considered as the Proof of the Nature of the Use of Arms in Law Enforcement
Different from legal rights and the legal status of sea areas, there are factors that are useful for
proving the nature of the use of arms in law enforcement. A number of authorities have suggested
various factors. They are the same, to a significant degree, as the factors that several authorities
have discussed for deciding the precise coverage of the prohibition of the use of force under
Article 2, Paragraph 4 of UN Charter.160① Actors
Actors are, in two ways, a factor to be considered: as actors of law enforcement and as the target
thereof. They may be both vessels and individuals. In dealing with law enforcement at sea, it is
not unreasonable to focus upon vessels.161
Regarding actors of law enforcement and the use of weapons concerned, one authority opinesthat without authorization, any boarding measures (by any actors) against foreign vessels mean
the threat of force (under Article 2, Paragraph 4 of the UN Charter). This could be justified
principally as an exercise of the right of self-defense.162 This position is understandable if it isbased upon the rigid interpretation of Article 2, Paragraph 4 of the UN Charter such that theprovision applies to law enforcement at sea.163 As explained above,164 this article does not takesuch a position. Rather this article is of the position that this provision does not prohibit any use
of weapons in an all-inclusive manner, and that it allows some room for the legal use of weapons.
Nevertheless, seriously taking into consideration the concern over the potential abuse of suchroom, as claimed by the aforementioned rigid interpretation, this article seeks to clarify the useof arms in law enforcement as much as possible, and to propose any possible tools for thoroughly
proving the nature of the use of arms in law enforcement.
Regarding actors that are the target of the law enforcement, these are commercial vessels,
warships and other government ships operated for non-commercial purposes.165 Later, Section IV
and Section V will conduct a special examination of the issue of vessels that enjoy immunity.

159

Section IV and Section V.

160

The factors are, for instance, the scale of the violence on both the side of the wrongdoers and thosesubjected to the use of weapons, the nature of the wrongdoers involved, the political intent of thewrongdoers, and the legal interests being infringed by the violence of the wrongdoers; see “Maritime
Security,” 49 and the footnote thereto.

161

Depending on domestic laws, ships and/or individuals are the targets of law enforcement.

162

Guilfoyle, op. cit., supra n. 54, 293.

163

See supra n. 54.

164

Section I, 3.

165

If the actors are militia, it may raise an inherent question. While this article does not go into detailon this question, see, for instance, Andrew Erickson and Conor Kennedy, “Countering Chinaʼs Third
Sea Force: Unmask Maritime Militia before Theyʼre Used Again,” The National Interest, 6 July 2016,
https://nationalinterest.org/feature/countering-chinas-third-sea-force-unmask-maritime-militia16860?page=0%2C1; James Kraska, “Chinaʼs Maritime Militia Vessels May Be Militar y Objectives
During Armed Conflict,” July 07, 2020, The Diplomat https://thediplomat.com/2020/07/chinasmaritime-militia-vessels-may-be-military-objectives-during-armed-conflict/.

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Reconsideration of the Distinction between the Use of Arms in Law Enforcement
and the Use of Force Prohibited by International Law—With an Analysis of the Inherent Significance of This Issue to Japan—② Character of the Actors
Frequently, when warships are involved either as actors of law enforcement or as the targets oflaw enforcement, the question arises as to whether the character of the actors, or the characterof the organs to which they belong, decides the nature of the measures and the nature of the useof weapons accompanying them. In this regard, as confirmed above, the recent jurisprudence
denies that the involvement of warships or military vessels alone determines that the measuresand the use of weapons are military in nature, although it admits that character is a factor to beconsidered.166
This issue relates to the definition of warships. 167 ITLOS did not have the oppor tunity
to consider Article 298, Paragraph 1 (b) of UNCLOS in the ARA Libertad Case (provisional
measures),168 which dealt with a case in which Argentinian naval vessels entered Ghanaian waters
on a training mission. Whether the naval vessels per se enjoy immunity can be questioned.169 One
authority opined that warships enjoy immunity, even if they are not militarily equipped, and even
if they are not conducting military activities.170 As explained above, this position may have an
impact on the determination of “military activities,” as far as the tribunals consider the entity with
its character implementing the measures and the use of weapons accompanying them.171
It is indispensable to remember that the jurisprudence examined above entertained the cases
before them in the special context of the alleged application of the “military activities” exception
for the compulsory jurisdiction under UNCLOS. It considered this issue as an interpretation of
Article 298, Paragraph 1 (b).172 Different to that, this article is searching for any tools for proving
the use of arms in law enforcement. For that purpose, it is important to take note of the wide
definition of warships with their military nature. This means that, depending on individual cases,
law enforcement conducted by warships without military equipment and without members of thenavy or marines on board may be alleged to be military activities and the use of force.173③ Factors that Decide the Nature of Situations
This article adopts the terminology “situations,” the nature of which is the same as that of themeasures involved. Therefore, in some sense, in a circular manner, self-defense situations arethose under which the use of force takes place,174 and law enforcement situations are those underwhich law enforcement measures are taken.175 A number of authorities have suggested various
factors that indicate the nature of situations.
These are the interests that the measures are aimed at protecting, such as safety, the good
166

The Detention Case (provisional measures), supra n. 66, para. 64. The Coastal State Rights Case, supra n.
66, para. 334.

167

Article 29 of UNCLOS provides for this.

168

The “ARA Libertad” Case (Argentina v. Ghana), (provisional measures), Order of 15 December 2012,https://www.itlos.org/fileadmin/itlos/documents/cases/case_no.20/published/C20_Order_151212.
pdf (hereinafter referred to as “the ARA Libertad Case”).

169

Damrosch, op. cit., supra n. 133.

170

Oxman, op. cit., supra n. 134.

171

This Section, 2.

172

Supra n. 98.

173

One authority has pointed out the lack of law enforcement vessels in many countries, and that, thus,
military vessels are used for law enforcement; see Kwast, op. cit., supra n. 4, 63–64.

174

Also, they may be described as situations under which Article 2, Paragraph 4 and/or Article 51 of the
UN Charter apply.

175

Also, they may be described as situations under which the law enforcement provisions of UNCLOS,
such as Articles 25, 73, and 110 apply.

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Atsuko Kaneharaorder of oceans, national security, conser vation and management of natural resources, andmarine environmental protection. Not only the national interests of the law enforcement States,
but also the common interests of international society are to be protected by law enforcement
measures that are taken in accordance with, for instance, the resolutions of the UN Security
Council. There could be a case in which the UN Security Council decides and even changes
the nature of situations by the collective intention of international society.176 Such indications ofcertain interests are very similar to those that are reflected by the rights and the legal status of
the sea areas as tools for proving the use of arms in law enforcement.177
Those interests may, to a certain degree, provide indications for identifying the character of aparticular situation. Nonetheless, as the aforesaid jurisprudence suggests, thorough considerationof the facts and factors in each case is critical for finally determining the nature of situations,and, thus, the nature of the measures and the nature of the use of weapons accompanying them.
In this regard, the use of the expression “violent acts at sea” reflects the same line of thinking
as this. “Violence” can have a wide meaning, spanning a violent act in committing a crime at sea
and the use of force, and it may change from one to the other with there even being violence inbetween.178
Thus far, this Section has examined the jurisprudence and various tools for proving the useof arms in law enforcement. The next Sections will analyze, as a special issue, the legal nature of
the measures and the use of weapons accompanying them to be taken by coastal States in theirterritorial seas against foreign vessels that enjoy immunity. This is an issue that may relate to therelationship between the jus ad bellum and the law of the sea. In addition, this issue has troubled
Japan for a long time as it has faced Chinese government vessels and warships that periodicallyenter Japan ʼ s territorial sea surrounding the Senkaku Islands. 179 After a succinct generalexamination, a particular consideration of Japanʼs case will follow.

IV. Measures by Coastal States against Foreign Vessels That Enjoy Immunity:
General Examination of the Issue Concerned
As for the immunity of government vessels and warships in foreign territorial seas, Article 32 of
UNCLOS reads:
With such exceptions as are contained in subsection A and in articles 30 and 31, nothing inthis Convention affects the immunities of warships and other government ships operated for
non-commercial purposes.
Thus, warships and government ships operated for non-commercial purposes (hereinafter

176

Regarding piracy and international terrorism, setting aside the issue whether the common interest of
the international society and/or the national interest of the victim States are in danger, the traditional
idea is to combat them through a law enforcement function. However, depending on the scale andseriousness of the circumstances, the UN Security Council has determined certain situations in whichinternational peace and security are threatened. On this issue, see Tullio Treves, “Piracy, Law of theSea, and Use of Force: Developments off the Coast of Somalia,” The European Journal of InternationalLaw, 20 (2) (2009), 400–401.

177

See this Section III, 3. (2).

178

Koichi Morikawa “Kaijo Boryoku Koi [Violent Act at Sea],” in Soji Yamamoto ed., Kaijo Hoan Hosei–
Kaiyo Ho to Kokunai Ho no Kosaku [Laws on Coast Guard̶Interplay between the Law of the Sea andDomestic Law], (Sanseido, 2009), 294.

179

See the Introduction, 2.

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Reconsideration of the Distinction between the Use of Arms in Law Enforcement
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referred to as “government ships”) enjoy immunity.180 The phrase “With such exceptions as
are contained in subsection A and in articles 30 and 31,” has raised complicated interpretativeand even confusing issues regarding the coverage of the immunity. Here, the purpose is not toconsider in detail such interpretative issues, while some will be examined. Rather, it will be simply
presupposed that warships and government ships enjoy immunity under Article 32.181 Measuresby coastal States of territorial seas may have different implications and impacts on the targets,
depending on whether they are warships and government ships.182
Article 30 of UNCLOS reads:
If any warship does not comply with the laws and regulations of the coastal State concerning
passage through the territorial sea and disregards any request for compliance therewith
which is made to it, the coastal State may require it to leave the territorial sea immediately.183
As far as warships hold immunity, when they violate the laws and regulations of the coastal Stateof a territorial sea, the latter can solely require them to leave the territorial sea.184 As far as thislimits the measures that coastal States are allowed to take, it can be said that Article 25185 does
not apply to warships, or that “the necessary steps” under Article 25, Paragraph 1 are confined
to asking the warships to leave the territorial sea. This is one of the interpretative issues that thephrase “Wits such exceptions as are contained in subsection A and in article 30 and 31” of Article
32 may raise. While under Article 30, there is no mention of government ships, this restriction on
the measures that the coastal State may take should be the same as in cases of warships.186
When warships are not violating the laws and regulations of the coastal State of a territorial180

As an examination of the significance of the immunity of warships, see Ingrid Delupis, “Foreign
Warships and Immunity for Espionage,” The American Journal of International Law, 78 (1) (1984),
53–57. Another authority discusses how the immunity of warships is derived from law enforcement
jurisdiction but not from prescriptive jurisdiction; see Isabelle Pingel, “Lʼimmunité des navires deguerre,” in La mer et son droit, Mélanges of ferts à Laurent Lucchini et Jean-Pierre Quéneudec, (A.
Pedone, 2003), 296, footnote, n. 29.

181

Regarding Article 32 in the context of the ARA Libertad Case, see Massimo Lando, “State Jurisdiction
and Immunity of Warships in the ARA Libertad case,” Japanese Yearbook of International Law, 58 (2015),
348–353.

182

As for consideration of this issue in a detailed manner, see Naoya Okuwaki, “Ryokai ni Okeru Gaikoku
Kosen ni Taisuru Shikko Sochi [Law Enforcement against Foreign Government Vessels],” in Kaiyo
Keneki no Kakuho ni Kakaru Kokusai Hunso Jirei Kenkyu (Dai 2 Go) [Case Studies on Maintenanceof National Interest at Sea (No. 2)], (Kaijo Hoan Kyokai, 2010), 1–4. As confirmed in the Introduction,
under Article 83 of the CCGL, Chinese coast guard ships perform defense operations. In this sense,
when coping with Chinese vessels, the distinction between warships and government ships may lose
its significance. For instance, in predicting the impact of measures taken by Japan with the use of
weapons, the issue whether they are against Chinese warships or government ships is not substantiallysignificant. Whichever the target of the measures may be, a serious and tense circumstance will inevitably
occur.

183

While this article will not elaborate on the issue, Article 236 of UNCLOS provides for the immunityfrom law enforcement measures for protecting the marine environment. See Oxman, op. cit., supra n.
134, 819-820. Regarding the use of weapons in law enforcement for marine environmental protection,
see Jinxing Ma and Shiyan Sun, “Restrictions on the Use of Force at Sea: An Environmental Protection
Perspective,” International Review of the Red Cross: War and Security at Sea, 98 (2) (2016), 515–541.

184

Some States have detailed rules for this requirement of leaving; see Tian Shichen, “The Legal Status of
Foreign Warships in Territorial Seas,” China Oceans Law Review, 2007 (2), 365–366.

185

Paragraph 1 of Article 25 reads:
The coastal State may take the necessary steps in its territorial sea to prevent passage which is not
innocent.

186

Regarding the possible different treatments of warships and government ships, see Okuwaki, op. cit.,
supra n. 182, 2–3.

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Atsuko Kaneharasea, there is a case in which their activities are prejudicial187 to the peace, good order or securityof the coastal State.188 In such a case, what measures could the coastal State take?189 Would Article
25 that allows coastal States to take “necessary steps” apply without the restriction being set forth
by Article 30? A literal interpretation of Article 30 would allow such an interpretation, whereby
Article 30 applies solely to the case in which foreign warships violate laws and regulations.
However, the issue regarding the relationship between the immunity of the warship and thecoastal Stateʼs right to take the necessary steps remains. Is it possible for the coastal State to takemeasures beyond asking the warship to leave, without infringing upon its immunity? Even if theanswer is positive, this would inevitably lead to heightened and aggravated tension between theStates concerned.190
As far as the immunity means immunity from any exercise of law enforcement measures,
irrespective of the degree of its coerciveness, even asking a warship to leave might be an
infringement of its immunity. If so, Article 30 is interpreted, as an exception, as allowing thecoastal State to ask the warship to leave, even though this is an infringement of its immunity. Herecomes the issue of the interpretation of Article 32, in respect to its phrase “With such exceptions
as are contained in subsection A and in articles 30 and 31. ” Without going into the detailed
examination, solely the confirmation of the following points is useful. On the one hand, the coastal
State may take the measures under Article 30 as an exception of the immunity. In other words,
the measures under Article 30 do violate the immunity, but the coastal State is allowed to takethem as an exception. On the other hand, it could be said that the measures under Article 30 do
not violate the immunity due to their non-coercive nature.
Even according to the interpretation of immunity in the strongest way, against a warshipthat does not violate the laws and regulations of the coastal State, as is the case that Article 30
assumes, but whose acts191 are prejudicial to the peace, good order, or security of the coastal
State, the coastal State could, at most, ask the warship to leave the territorial sea. Article 30 might
apply, in some sense, mutatis mutandis, to such a case. If a request to leave does not violate theimmunity, there would be no problem of the violation of the immunity by such a request. Then,
can the coastal State take more coercive measures?
From this articleʼs perspective, the point is not the coverage or applicability of the immunity,
but the nature of the use of weapons accompanying the measures, if the measures of the coastal
State infringe upon the immunity of warships. In other words, the question is whether there is any
justification for the coercive measures even with the use of weapons and, therefore, whether thenature of the measures can remain that of law enforcement, with the nature of the use of weapons
187

The existence, itself, of warships may be prejudicial. This is the traditional issue regarding the meaningof “non-innocence,” and the issue of the relationship between Paragraphs 1 and 2 of Article 19 of
UNCLOS. However, all ships have the right of innocent passage under Article 17 of UNCLOS, andaccording to several authorities, “non-innocence” should be determined by the concrete activities underParagraph 2 of Article 19, not by the kinds of vessels involved. This article will not go into the details of
this. Here, it is enough to confirm that the activities of warships can be presupposed to be prejudicial tothe peace, good order or security of the coastal State.

188

As for a detailed analysis of this issue, see Froman, op. cit., supra n. 98, 660–665.

189

Regarding this point, see Francesco Francioni, “Use of Force, Military Activities, and the New Lawof the Sea,” in A. Cassese ed., The Current Legal Regulation of the Use of Force, (Martinus Nijhoff
Publishers, 1986), 264.

190

As will be examined later, if the use of weapons accompanies the measures by the coastal State, thenature of the use of weapons should be considered in such a tense circumstance.

191

Depending on the interpretation of Article 19, Paragraph 1, and of the relationship between Article 19,
Paragraph 1 and Paragraph 2, the presence or existence of foreign warships may be prejudicial to thepeace, good order, or security of the coastal State.

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being the use of arms in law enforcement. It is not to mention, however, that the possibility of
the worst-case scenario is not denied, which means the change of the situation from that of law
enforcement to that of self-defense.
As for the justification for the use of weapons in law enforcement, in such a case, the balanceof interest is to be considered.192 On the side of the warship, an infringement of its immunity
would breach its dignity and sovereignty.193 On the side of the coastal State, the activities of thewarship, which are prejudicial to the peace, good order or security, would infringe upon thoseinterests and the coastal Stateʼs sovereignty over the territorial sea and cause potential harm to
its security.194 If the coastal State is not allowed to take any enforcement measures against thewarship other than a request to leave from its territorial sea, these interests and sovereignty
would be infringed upon. In addition, even if the warship should be allowed to maintain its
immunity, there still remains the issue of the potential abuse of its immunity.195
In contrast, as a dif ferent position, in such a case, the immunity could be denied. The
sovereign immunity is based upon the most fundamental principle of respect for sovereignty
under international law. In the case concerned, the activities of the warship are prejudicial to thepeace, good order, or security of the coastal State, which means posing a risk to its sovereignty.
When the coastal Stateʼs sovereignty is in danger of or in fact being infringed upon, it is notreasonable for it to be imposed with respecting the immunity of the warship. The sovereigntyof the warship and that of the coastal State are evenly at stake. Considering this, it is not fair torequire the coastal State to respect the immunity of the warship, and accordingly the sovereigntyof the warship.196
The same could be said for cases in which the warship violates the laws and regulations of thecoastal State and at the same time poses a risk to the peace, good order, or security of the coastal
State, thus, a risk to its sovereignty.197 In such cases, beyond the restriction under Article 30, thecoastal State should be allowed to take measures to protect its sovereignty.
192

It is necessary to precisely examine immunity at sea under the law of the sea, and that under generalinternational law. Furthermore, immunity at sea may have different meanings depending on thesea areas concerned, as the interests of the States that take law enforcement measures may change
depending on the sea area concerned, such as their territorial seas, exclusive economic zones, or highseas. Therefore, Article 32, on the one hand, and Articles 95 and 96, on the other hand, require different
considerations when examining the interests at stake of the States concerned. For such an analysis, seeFrancioni, op. cit., supra n. 189, 362–373.

193

In the Detention Case (provisional measures), ITLOS, referring to the ARA Libertad Case, said:“(A) warship, as defined by article 29 of the Convention, ʻis an expression of the sovereignty of theState whose flag it fliesʼ. This reality is reflected in the immunity it enjoys under the Convention andgeneral international law. The Tribunal notes that any action affecting the immunity of warships iscapable of causing serious harm to the dignity and sovereignty of a State and has the potential toundermine its national security.”	Ibid., para. 110. It deserves attention that the tribunal mentions both immunity under UNCLOS andthat under general international law. It might recognize the difference between the immunity under
UNCLOS and that under general international law.

194

Regarding the interests of the coastal States of territorial seas, see Soji Yamamoto, “Mugai Tsuko ni
Ataranai Ryokai Shinpan [Invasion of Territorial Seas by Non-Innocent Passage],” in Wagakuni no Shin
Kaiyochitsujo [New Maritime Order of Japan], (Kaijo Hoan Kyokai, 1990), 72–76.

195

Roma Sadurska, “Foreign Submarines in Swedish Waters: The Erosion of an International Norm,” Yale
Journal of International Law, 10 (1984), 55.

196“Japanʼs Integrative Position,” 1626–1630.

197

As for a similar position, see Soji Yamamoto, “Mugai Tsuko Ken to Engankoku no Kankatsuken
Koshi no Genkai [Innocent Passage and the Limits on the Exercise of the Coastal State Jurisdiction],”Wagakuni no Shin Kaiyochitsujo [New Maritime Order of Japan], 2 (Kaijo Hoan Kyokai, 1989), 84.

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Then, the critical remaining issue is whether such measures of the coastal State, even withthe use of weapons, could retain the nature of law enforcement, and whether the use of weapons
could also retain the nature of the use of arms in law enforcement.
In this regard, a number of authorities mention the right of self-defense, particularly in
relation to the use of weapons accompanying the measures that are assumed, here, to be taken
by coastal States.198 As a similar issue, authorities refer to non-innocent passage of a foreign
submarine in territorial sea,199 and an onboard measure by a State against foreign government
vessels and warships suspected of engaging in piracy in exclusive economic zones.200 In addition,
the following question is raised: When a warship conducts marine research but it is not “marine
scientific research” that falls under UNCLOS,201 what is the nature of the measures that can betaken against it by the coastal State of the exclusive economic zone?202
In a comparative analysis of these various facts and cases, not to mention a thoroughexamination thereof, not only the interests at stake of the States concerned, but also thefollowing points should be carefully considered in a detailed manner. These are the scale of thecoerciveness of the measures and that of the use of weapons accompanying them on the side of
the coastal State that takes the measures and, on the side of the warships, the persistent nature of
the violations of the laws and regulations of the coastal State,203 and the continuous existence of
the warship in the territorial sea irrespective of the request for it to leave.204
Thus, several authorities have discussed the right of self-defense of the coastal State205that takes measures with the use of weapons against warships and government ships enjoying
immunity.206 Is such a use of weapons solely characterized as an exercise of the right of self-

198

As for discussing such an issue, see the following authorities: Oxman, op. cit., supra n. 134, 815; Delupis,
op. cit., supra n. 180, 72; Lowe, op. cit., supra n. 149, 176 and 180. As for a prudent position on this point,
see Okuwaki, op. cit., supra n. 182, 6.

199

Sadurska, op. cit., supra n. 195, 34–38.

200

Oxman, op. cit., supra n. 134, 824.

201

It is problematic that UNCLOS does not give any clear definition of “marine scientific research.”

202

Oxman, op. cit., supra n. 134, 846. A hypothetical case is mentioned in which activities that are disguised
as “marine scientific research” could be conducted by Chinese government vessels and said research
activities may mean preparation for a war, which would infringe upon the territorial integrity of Japan;
see Okuwaki, op. cit., supra n. 182, 10.

203

R. R. Churchill and A. V. Lowe, The Law of the Sea, 3rd ed., (Juris Publishing, Manchester University
Press, 1999), 99; McLaughlin, op. cit., supra n. 143, 19; Sadurska, op. cit., supra n. 195, 55.

204

In that case, the warship should lose its immunity; see Akira Mayama, “Ryokai ni Aru Gaikoku Gunkan
ni Taisuru Kyoryokuteki Sochi ni Kansuru Oboegaki [Memorandum on Forcible Measures against
Foreign Warships in Territorial Sea],” Kokusai Anzenhosho [International Security], 35 (1) (2007),
46. Mayama examines the coercive measures against warships as those holding the nature of law
enforcement, ibid., 47.

205

In addition to the authorities cited at supra n. 198 above, see Shearer, op. cit., supra n. 81, 441.

206

In a different context, the use of force is discussed in cases in which there are threats from theglobal commons, Stuart Kaye, “Threats from the Global Commons: Problems of Jurisdiction and
Enforcement,” Melbourne Journal of International Law, 8 (1) (2007), 185 et seq.

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defense? 207 Is there a dif ferent possibility to explain such a use of weapons? 208 It may beunreasonable to require the coastal State to satisfy the requirements for an exercise of the right ofself-defense.209 Herein lies the issue of the relationship between the law of the sea and the law of
the use of force.210 It is far beyond this articleʼs examination to thoroughly discuss such a difficult
issue.211 However, the following points could be mentioned.212
If such a use of weapons is an exercise of the right of self-defense, it needs to satisfy therequirements for exercising said right.213 Rather, as an issue under the law of the sea, such a useof weapons could be characterized in a different manner from the right of self-defense under
the jus ad bellum. It could be defined as a sort of right of coastal States to take law enforcement
measures with a use of weapons for protecting their sovereignty, peace, good order, or security
in relation to their territorial seas. Such a right of coastal States does not necessarily go beyond
the sphere of the law of the sea, but is instead under it, or it might be called the right existing inbetween or in the gap between the law of the sea and the jus ad bellum.214 Furthermore, persistentviolations of the laws and regulations of coastal States and repeated disregard for requests toleave on the side of warships and government ships are not only infringements of these values of
the coastal States, but also challenges against the regime itself of the territorial sea as a core pillarof the law of the sea, as well as territorial sovereignty as a core pillar of international law.215
If one takes this position that admits certain justification for such a use of weapons, thecritical issue is how to prevent the abuse of such a right to use weapons in order to maintain theimportant significance of the prohibition of the use of force, which has fundamental value forinternational law. Providing a direct and perfect solution to this issue would be tremendously
dif ficult. There are standards for evaluating the legality of the way to use of arms in law
enforcement, such as the standards of reasonableness, necessity, and proportionality thatinternational practice, including the jurisprudence, has established. These standards regulate
the way to use weapons, and they do not provide direct justification for the use of weapons
207

One authority sets forth the categorization of the laws applicable to the use of force depending on thelegal basis for actions in the limited context of interception under the Proliferation Security Initiative;
see Craig, op. cit., supra n. 80, 96–110.

208

Regarding the Pueblo incident and similar ones, see George H. Aldrich, “Questions of International Law
Raised by the Seizure of the U.S.S. Pueblo,” Proceedings of the American Society of International Law at
Its Annual Meeting (1921–1969), 63 (1969), 2–6; Francioni, op. cit., supra n.189, 365–366; Sadurska, op.
cit., supra n. 195, 34–38.

209

Regarding this point, see Mayama, op. cit., supra n. 204, 48–50; Delupis, op. cit., supra n. 180, 72;
Froman, op. cit., supra n. 98, 674 and 683; Francioni, op. cit., supra n. 189, 364.

210

This article does not touch upon the legal standards that regulate the way to use of weapons either as
law enforcement or self-defense. The latter belongs to jus in bello. Thus, here, this law can be said to be
jus ad bellum.

211

For instance, see Lowe, op. cit., supra n. 149; Wolfrum op. cit., supra n. 149.

212

As a related issue, there is discussion of whether the use of weapons against a commercial ship without
legal justification or without proportionality, would become the use of force against the flag State of thetarget ship; see Wolff Heintschel von Heinegg, op. cit., supra n. 101, 460–426.

213

The ICJ dealt with the requirements for the exercise of the right of collective self-defense in the
Nicaragua Case (merits), supra n. 50, para. 232. This ar ticle will not go into the details of therequirements to be satisfied for an exercise of the right of self-defense, both under Article 51 of the UN
Charter and under general international law.

214

Francioni, op. cit., supra n. 189, 363–367; Dale G. Stephens, “The Impact of the 1982 Law of the Sea
Convention on the Conduct of Peacetime Naval/Military Operations,” in Donald R. Rothwell ed., Law of
the Sea, (Edward Elgar Publishing Limited, 2013), 294–296.

215“Japanʼs Integrative Position,” 1624.

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itself. Nonetheless, it could be reasonably expected that they should have a certain degree ofsignificance for preventing the abuse of such a right to use weapons exercised by coastal States
in taking measures against warships and government ships that enjoy immunity.216 In addition,
based upon a comparative analysis of similar facts and cases that have been already suggested byvarious authorities as seen above, and by balancing the interests at stake of the States concerned
and thoroughly considering the various facts in each case, it could be possible to determine thelegality of such a use of weapons. These existing standards and possibly the accumulation of
actual practice could be expected to discharge the function of preventing the abuse of such a useof weapons.
This ar ticle is examining the law enforcement measures and the use of arms in law
enforcement. From this perspective, here, it has sought for the justification for a use of weapons,as that accompany law enforcement measures, against foreign warships and government vesselsthat infringe the sovereignty and security of the coastal State. It is not to mention that as theworst-case scenario, the situation would change from that of law enforcement to that of selfdefense, and in that case, the coastal State would exercise the right of self-defense.
The next and last Section will succinctly introduce Japanʼs position in relation to this issue.

V. Japan’s Position with Respect to Measures to Be Taken against Warships andGovernment Ships That Enjoy Immunity217
The Introduction of this article succinctly explained the circumstance in which Japan has been
facing Chinaʼs warships and government ships in Japanʼs territorial sea surrounding the Senkaku
Islands.218
For more than a decade, China has periodically sent its government vessels and warships toJapanʼs territorial sea surrounding the Senkaku Islands.219 These vessels enjoy immunity under
Article 32 of UNCLOS. As examined above, if Japan takes coercive measures, in some cases evenusing weapons,220 authorities indicate that the scenario would change from one under the lawof the sea to one to be regulated by the law on the international peace and security. Based upon
the analysis in the previous section, various considerations are needed to legally evaluate such a
possible use of weapons.
What has China conducted in Japanʼs territorial sea surrounding the Senkaku islands? China
has, as a matter of fact, frequently dispatched its coast guard vessels and military ships to thesesea areas.221 There, China has taken law enforcement measures against Chinese fishing boats andeven against Japanese fishing boats.222 This is based upon its understanding that the sea areas
216

Stephens, op. cit., supra n. 214, 309; Francioni, op. cit., supra n. 189, 363–365.

217

This author has already introduced Japanʼs position elsewhere, in a full manner, and the gist of it will begiven in the coming Section. See also Kanehara, op. cit., supra n. 28.

218

As for coast guarding of Japanʼs territorial sea, see Atsuko Kanehara, “Ryokai Keibi ni Kakaru Ho Seibino Teigen [A Proposal on Indispensable Legislative Measures for Coast Guarding of Japanʼs Territorial
Sea],” Sophia Law Review, 65 (4) (2022), 11–57.

219

See “Japanʼs Integrative Position,” 1594–1595.

220

Some measures, such as shouldering, do not necessarily accompany the use of weapons but are
coercive.

221

For an overview of the situation, see Ministry of Foreign Affairs of Japan, Status of Activities by Chinese
Government Vessels and Chinese Fishing Vessels in Waters Surrounding the Senkaku Islands (26 August2016), https://www.mofa.go.jp/files/000180283.pdf.

222

Jun Kitamura, “Tracking Japanese Fishing Boats off the Coast of the Senkaku Islands, Making a New
Established Fact that China has Struck,” The Asahi Shimbun Globe, 18 June 2020, https://globe.asahi.
com/article/13461863.

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surrounding the islands concerned are its territorial sea.223 In addition, Chinese fishing vessels
also come to these sea areas. Their number has even reached a few hundreds.224 Furthermore, it
is said that these fishing vessels are, in some cases, also militia vessels.225
With respect to the interests at stake, Chinese warships and government ships (whereappropriate, they will be designated as “Chinese vessels”) enjoy immunity under Article 32 of
UNCLOS. On the one hand, if Japan takes measures against them beyond that which it is allowed
to take under Article 30, and, as long as Chinese vessels maintain said immunity, it would infringe
upon Chinaʼs sovereignty. On the other hand, the activities of the Chinese vessels have violated
Japanʼs sovereignty,226 as they have conducted law enforcement in Japanʼs territorial sea. The
huge number of Chinese fishing boats are said to be militia, in which case, Japanʼs peace andsecurity are seriously endangered.
Setting aside the issue of the compatibility of the activities of Chinese vessels with Japanʼs laws
and regulations, there is no doubt that they are prejudicial to the peace, good order or securityof Japan under Article 19, Paragraph 1 of UNCLOS. In addition, Chinese vessels have entered
Japanʼs territorial sea “periodically,”227 and their activities and disregard for Japanʼs requests toleave have been persistent.
Japan has thus far repeated its requirement that the Chinese vessels leave Japanʼs territorialsea.228 No further measures have been taken by the JCG. Japan made a cabinet decision on 14
May 2015229 to cope with foreign vessels conducting non-innocent passage in Japanʼs territorial sea
through maritime police operations by the JMSDF.230 Considering the interests at stake, as well as
the facts of the persistent nature of the activities of Chinese vessels and their persistent disregard
for Japanʼs request to leave according to Article 30 of UNCLOS, Japan could take more coercive
measures, even those with the use of weapons, depending on the concrete circumstances. As
Chinese vessels are seriously infringing upon Japanʼs sovereignty, the immunity of these vessels
could be denied. The principle of immunity is based upon respect for sovereignty. As long as
the Chinese vessels disregard, vis-à-vis Japan, this fundamental value of sovereignty underinternational law, immunity should not be conferred upon them.
223

China insists that Japanese fishing boats entered the territorial sea of the Diaoyu Islands; see Ministryof Foreign Affairs of the Peopleʼs Republic of China, Wang Yi Reiterates Stance on Diaoyu Islands (25Nov 2020), http://ch.china-embassy.gov.cn/ger/zgxw/202011/t20201127_3208257.htm. (“The fact
is that recently some Japanese fishing boats of unknown origin have repeatedly entered the sensitive
waters off the Diaoyu Islands, and China has to make necessar y response. On this issue, Chinaʼsposition is clear. The Chinese side will continue to firmly safeguard its sovereignty and at the same time
proposes three hopes.”)224

For instance, according to a report issued by the JCG, two hundred to three hundred Chinese fishingboats have entered the territorial sea surrounding the Senkaku Islands. See Ministry of Defense ofJapan, slideshow, “Chinaʼs Activities in the South China Sea,” (March 2021), https://www.mod.go.jp/
en/d_act/sec_env/pdf/ch_d-act_b_e_210421.pdf.

225

Regarding the serious issue that militia vessels would cause, see supra n. 165.

226

Kanehara, op. cit., supra n. 28.

227

See supra n. 19.

228

As for the possible impact of these measures on Japanʼs position that there is no dispute over the
territorial sovereignty of the Senkaku Islands between China and Japan, see “Japanʼs Integrative
Position,” 1616–1618, 1623–1624, 1629–1630.

229

https://www.cas.go.jp/jp/gaiyou/jimu/pdf/gaikokugunkantaisho/pdf (in Japanese).

230

See supra n. 23. Thus far, except for one example, no maritime police operation has been realized inaccordance with the decision. Regarding the functions of the navy and the coast guard in the U.S., see
Douglas Daniels, “How to Allocate Responsibilities between the Navy and Coast Guard in Maritime
Counterterrorism Operations,” University of Miami Law Review, 61 (2) (2007), 467–508.

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Atsuko KaneharaWith respect to the measures that Japan could take, Japanʼs position has been unclear. For
instance, Japanese authorities gave interesting remarks in the Diet. When the possible use of
weapons against foreign government vessels and warships was discussed, a question was asked
as to whether such a use of weapons would become harmful shooting, and if that were the case,whether such a use of weapons constitute a hostile act. Without mentioning the meaning of law
enforcement under domestic law and that under international law and the relationship between
the two, Mr. Masataka Okano, the then Director-General, International Legal Affairs Bureau,
Ministry of Foreign Affairs, answered:
From the perspective of international law, such an act is defined as law enforcement in Japanʼsterritorial sea.231
When it was asked whether law enforcement acts can cope with such a case of an infringementof Japanʼs sovereignty in which, for instance, the crew of the vessels of Chinaʼs Coast Guard landon the Senkaku Islands (in the Diet, such a case was previously recognized as an infringementof Japanʼs sovereignty by the Minister for Foreign Affairs), again, without any explanation of law
enforcement under domestic law and that under international law, Mr. Masataka Okano, the thenDirector-General, International Legal Affairs Bureau, Ministry of Foreign Affairs, said:
What is important here is whether Japan conducts activities in conformity with internationallaw. The basic point is that Japan conducts law enforcement activities that are permitted byinternational law (emphasis added).232
As mentioned above, this article is examining the law enforcement measures and the useof arms in law enforcement. Thoroughly under this framework of examination, it has soughtfor the justification for a use of weapons against foreign warships and government vessels that
infringe the sovereignty and security of the coastal State. In addition, at least, for the preventionof escalation, law enforcement measures are preferable to self-defense measures.233 Nonetheless,as the worst-case scenario, it could not be denied that the situation would change from that of law
enforcement to that of self-defense, and in that case, Japan, as the coastal State, would exercise
the right of self-defense. The remarks reproduced here mentioned law enforcement by Japan.
Nonetheless, there is no clarification of the reason why such a use of weapons in the context
concerned has the nature of the use of arms in law enforcement, not that of the use of force ofthe right of self-defense. More fundamentally, they do not indicate any understanding of theimportance and difficulty for Japan to maintain the nature of law enforcement of the measures
to be taken by it, in seriously considering the possible change of the situations from the law
enforcement to the self-defense that is, in reality, strongly expected.

Conclusion
This article re-considered the distinction between the use of arms in law enforcement and theuse of force prohibited by international law unless justified mainly by the right of self-defense.
Since this authorʼs previous work on this distinction, further re-examination has come to berequired. This is because the wide understanding of maritime security has been, in reality, firmly
established, thereby making it tremendously difficult to make said distinction.
Nonetheless, as long as the difference in the international rules is maintained, dependingon the two kinds of the use of weapons under international law, this distinction still very muchdeserves continuous analysis.
231

Minutes of the Committee on Foreign Affairs and Defense, House of Councillors, the 204 th Session, No. 7 (15April 2021), 8. For its English translation by this author, see Kanehara, op. cit., supra n. 28, [II-4-a].

232

Minutes of the Committee on Foreign Affairs and Defense, House of Councillors, the 204 th Session, No. 7 (15April 2021), 8–9. For its English translation by this author, see Kanehara, op. cit., supra n. 28, [II-4-b].

233

See supra n. 20.

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Reconsideration of the Distinction between the Use of Arms in Law Enforcement
and the Use of Force Prohibited by International Law—With an Analysis of the Inherent Significance of This Issue to Japan—

In addition, while this ar ticle left some issues for future works, the issue of the firm
establishment of the international regulation remains with respect to the use of arms in law
enforcement and the use of force prohibited by international law unless principally being justified
as an exercise of the right of self-defense.234 Furthermore, it would be indispensable to conduct a
more detailed examination regarding the relationship between the law of the sea regulating law
enforcement at sea, on the one hand, and the law on the international peace and security,235 on theother hand.
As a special issue, if a coastal State of a territorial sea takes coercive enforcement measures,
even with the use of weapons, against warships and government ships that are enjoying immunity,
several authorities have pointed out that the scenario would change from one under the law of thesea to one under the law on the international peace and security.
In this regard, as this article focused upon the use of arms in law enforcement, it examined
the justification for the use of weapons against foreign warships and government ships, as theuse of arms in law enforcement. It does not exclude the worst-case scenario of the change of thesituation from that of law enforcement to that of self-defense. However, without going into theself-defense situation, Japan, as the coastal State, should have possibility to legally use weapons as
the use of arms in law enforcement. This article sought for the justification for such a use of armsin law enforcement. For prevention of escalation also sets forth the justification for the forcible
enforcement measures. As indicated above in the previous Section IV, there should be othersimilar examples to this example of law enforcement with the use of weapons against foreign
vessels enjoying immunity. The accumulation of international practice and its theoretical analysis
are strongly expected. That will help to derive the international rules that regulate the use of
weapons in such incidents so as to avoid, as much as possible, the abuse of the use of weapons
under the fundamental principle of international law to prohibit the use of force.
This issue of law enforcement against foreign warships and government vessels has troubled
Japan almost every day in relation to China in the East China Sea. Under the particular legal
circumstance with Article 9 of the Constitution of Japan, and the strict distinction between law
enforcement and self-defense,236 how to most effectively protect its sovereignty and territorial
integrity has continued to be an urgent agenda for Japan to cope with.237 As introduced above,
judging from the discussion in the Diet, the official position of the Japanese government has
not been adequately determined, yet. The Japanese government needs to justify its measuresagainst Chinese warships and government ships, not only under its domestic laws but also underinternational law.
In this regard, the fact that the CCGL of 2021, under Article 83,238 enables Chinese coast guard
vessels to take defense measures, and the fact that the scenario of law enforcement under the lawof the sea can immediately change to that of jus ad bellum, are serious sources of concern. This isthe very reality that Japan has been facing.

234

See, for instance, Dieter Fleck, “Rules of Engagement for Maritime Forces and the Limitation of the Useof Force under the UN Charter,” German Yearbook of International law, 31 (1988), 165–186.

235

When focusing on the justification of such a use of force, it is an issue of jus ad bellum.

236

Thus, the issue of so-called “grey zones” is dealt with in this inherent framework of Japanʼs domestic
laws. As for the discussion on grey zones in Japan, see Koichi Morikawa, op. cit., supra n. 49 (Gurei
Zon) 29–38; “Maritime Security,” 51–52.

237

Kanehara, op. cit., supra n. 28, and 217.

238

See the Introduction, 2.

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