New naval anti-piracy tactics – pepper spray and “domestic” riot control

[Cross-posted from The Trench]

Yesterday the Smithsonian “Smartnews” site featured the article Robot Ships And Pepper Spray—the Latest in Pirate-Fighting Tech. According to the piece, UK researchers are actively looking into mobilising capsaicin – the active ingredient in pepper spray – to fend off pirate attacks at sea:


The age of naval battles between huge ships on the high seas seems to have passed into distant memory. Instead, some of the most devastating attacks on giant vessels in recent years have been executed by boats small enough to get through the larger ships’ defenses.

But now, governments around the world are working on technology designed to stop these attacks. In the U.K, researchers are working on a remote monitoring system—called the MATRiX system—that resituates the traditional responsibilities of a lookout to land-bound control rooms. The system has a connected network of anti-pirate deterrents attached to the outside of the ship. If a threat is detected, the deterrant [sic] system releases two relatively simple tools—nets that will catch in the propellers of attacking boats and a fog of capsaicin, the active ingredient in pepper spray (and bear repellent).


My question is: how does that fit with international law?

It stretches the understanding of non-prohibited purposes as defined in Article II, §9(d) of the Chemical Weapons Convention (CWC), which allows the use of riot control agents for law enforcement purposes, including domestic riot control. The concept of “law enforcement” is vague in the CWC and efforts are underway to clarify the notion in the context of various research and development activities concerning incapacitants.

In this particular case, however, it seems that not even law enforcement officials would  the responsible for the decision to release the capsaicin against pirates (unless they are the ones sitting in “land-bound control rooms”). The afore-mentioned article suggests that the device would be deployed by the  merchant ship under attack. Even if law enforcement officials would be at some land-based centre, would they be able to override the captain’s authority or would they just give the captain the green light to activate the system when needed? If the captain must call in authorisation from land, what country’s jurisdiction would come into play? The country under whose flag the ship is sailing? The country on whose territory the control rooms are located? The country whose nationality the law enforcement officials possess?

In light of the ongoing privatisation of security (who actually uses force to defend the ships against attacks? who sits in the land-based control rooms?), the blurring of boundaries between armed conflict and counter-terrorism / -crime operations, and the banalisation of riot control agents, it would appear that legal clarity about this new contraption should be established by the relevant national authorities and the international community (represented by the Organisation for the Prohibition of Chemical Weapons—OPCW).

Having said that, capsaicin is a toxin—a poison produced by a living organism. As such the legitimacy of its application is also covered by the Biological and Toxin Weapons Convention (BTWC). That treaty does not distinguish between whether the compound was derived from the chili pepper or produced synthetically. More importantly, however, the BTWC does not make an exception for law enforcement purposes. This leaves the question as to whether “law enforcement” can be considered to be one of the “other peaceful purposes” in Article I.

As it stands now, nobody has really been able to give me a sound explanation why the provisions of the CWC should supersede those of the BTWC.

I am open to good legal arguments.


13 Comments on “New naval anti-piracy tactics – pepper spray and “domestic” riot control”

  1. Dan Joyner says:

    Fascinating. It brings to my mind this case in which a U.S. federal court found the conservation group known as “Sea Shepherds” to have committed acts of piracy for doing things very similar sounding to what you have described here, Jean-Pascal.

    Click to access 1235266.pdf

    • Wang Tingliang says:

      Professor Dan Joyner mentioned in his comment the US case: Institute of Cetacean Research v. Sea Shepherd Conservation Society, 725 F.3d 940. When I was reading this article, I also thought of that case.

      Further, there is a very similar case held in the Belgium Court of Cassation, namely, Castle John and Nederlandse Stichting Sirius v. NV Mabeco and NV Parfin 77 ILR 537. This case is also concerning an environmental group known as “Greenpeace”, which has committed acts of piracy. In the court’s language: “Members of the environmental group ‘Greenpeace’ took action on the high seas against two vessels engaged in the discharge of noxious waste, in order to attract attention to the harmful effects of such discharge at sea. The action included boarding, occupying and causing damage to the two vessels.”

      Wang Tingliang
      (A student of Dr. James Fry’s course “Arms Control and Disarmament Law” at University of Hong Kong)

  2. Wang Tingliang says:

    Dr Jean Pascal Zanders, the author of this article, has asked a series of questions concerning the issue of jurisdiction: “if the captain must call in authorization from land, what country’s jurisdiction would come into play? The country under whose flag the ship is sailing? The country on whose territory the control rooms are located? The country whose nationality the law enforcement officials possess?”

    However, with due respect, I do not think it is quite necessary to ask which state’s jurisdiction would come into play. Since piracy is well recognized as a “universal crime” subject to universal jurisdiction, every state can exercise jurisdiction on ships or persons committing piracy. [see, for example Article 19 of Convention on the Highs Seas, Article 105 of United Nations Convention on the Law of the Sea, Lotus case (France v. Turkey), Series A, No.10, 1927 P.C.I.J. 65, 70 (Moore, Dissenting Opinion); In re Piracy Jure Gentium, 1934 A.C. 586, 589; Malcolm N. Shaw, International Law (6th ed., 2008, Cambridge University Press), 615-616, 668] Therefore, in my opinion, if the captain must call in authorization from land, he can call the authority of any state. All the choices the author has listed, namely, the state under whose flag the ship is sailing, the state on whose territory the control rooms are located, the state whose nationality the law enforcement officials possess, are acceptable under international law. The captain may choose one which he finds convenient and appropriate.

    Wang Tingliang
    (A student of Dr. James Fry’s course “Arms Control and Disarmament Law” at University of Hong Kong)

    • JP Zanders says:

      Dear Mr Tinglian, thank you for your comment. I appreciate your references to the Convention on the High Seas and the Law of the Sea. My point, however, has less to do with the issue of piracy than with the lawful authority to use a toxic chemical as a tool to protect the ship under attack by pirates.

      The Chemical Weapons Convention prohibits the use of chemical weapons under all and any circumstances. Tear gas and pepper spray are by default chemical weapons. The CWC has a caveat for “law enforcement purposes, including riot control”. However, it does not clarify its understanding of law enforcement. The issue has already come up a few times with respect to peacekeeping and -enforcement operations.

      Furthermore, the CWC requires the enactment of national implementation legislation, part of which includes criminalisation and penalisation. In this respect, any national of a party to the CWC, whether acting on the state party’s territory or abroad, can be held accountable for any act that contravenes the provisions of the CWC.

      So, my question is whether the captain of a ship can be viewed as a law enforcement authority in sense used in the CWC (bearing in mind that he negotiators allowed the caveat for capital punishment). If, as the cited article suggests, he requires authorisation from some land-based centre, then my follow-on question is where that centre derives its authority from, particularly if such a centre were to be staffed by a private security contractor? But even if it were government-run, chances are that the interlocutors have different nationalities.

  3. Megan M says:

    Although JP Zanders’ original post did not focus on the law of the sea, this article and the comments above highlight the potential legal issues raised by the interaction between the United Nations Convention on the Law of the Sea (UNCLOS) and the Chemical Weapons Convention (CWC).

    In his post, JP Zanders posed the question of which party would be responsible for a potential counter-attack against pirates involving chemical incapacitants. He highlighted the increasingly blurred lines between private and public actors and the privatization of security. With due respect, I agree with Wang Tingliang that the issue of attribution of responsibility is not as relevant under the UNCLOS regime. Under this treaty, only state vessels may legally seize pirate ships. According to article 107 of UNCLOS, “a seizure on account of piracy may be carried out only by warships or military aircraft, or other ships or aircraft clearly marked and identifiable as being on government service and authorized to that effect.” It is arguable that due to its disabling effects the use of capsaicin on a suspected pirate ship would amount to seizure of the ship. Therefore, only warships or ships on government service would be legally able to use capsaicin seize the ship.

    In my opinion, the issue is not whether the flag state or state of nationality will be responsible under international law. Rather, the issue is whether the term ‘law enforcement’ under the CWC encompasses law enforcement on the high seas, or whether it only pertains to law enforcement within the domestic sphere. A related issue is whether a counter-attack involving the use of capsaicin against a suspected pirate ship would qualify as a military action or an action of law enforcement (and therefore be exempt under article II(9) of the CWC). The use of the word ‘domestic’ within the phrase ‘domestic riot control purposes’ under article II(9) of the CWC might suggest that the ‘law enforcement’ exemption under the CWC refers to domestic law enforcement. Given the international context, is the use of a chemical weapon on the high seas more akin to military action than domestic riot control? If so, the exemption under article II of the CWC would not encompass enforcement of international law on the high seas, and the use of capsaicin to seize a suspected pirate ship would be illegal.

    • JP Zanders says:

      Dear Megan, thank you for your comment. This gets into deep argument about concurrent and competing legal systems, and I will leave that to lawyers.

      By virtue of Article I, 1(b) of the CWC the use of chemical weapons is prohibited under any and all circumstances. As you rightly note, the concept of ‘law enforcement’ (which is wider than ‘domestic riot control’) is ill defined in the CWC. All that we know is that nationals of a state party are banned from undertaking any activities that banned to a state party. So, what the question comes down to is how two international legal regimes interact with each other.

      I can recommend you a book published by the OPCW two years after entry intro force:
      “Treaty Enforcement and International Cooperation in Criminal Matters: With Special Reference to the Chemical Weapons Convention” by Rodrigo Yepes-Enríquez (Editor), Lisa Tabassi (Editor), 1999, which addresses these types of questions directly.

      In particular, I wish to point out the conclusion of the chapter by Burke-White (p. 86):

      In the past 10 years the options available for the prosecution of serious international crimes such as a chemical weapons attack have expanded greatly. This proliferation of fora for prosecution has provided new mechanisms to ensure that the most serious international criminals do not escape justice. However, unlike domestic criminal justice systems, there are no clear lines and procedures to determine which courts will hear which cases, nor is there a hierarchy of courts as provided by the domestic appeals process. Instead, the emerging system of international criminal law consists of a horizontal network of courts with potentially concurrent and competing claims to jurisdiction. The challenge which lies ahead is to devise and institutionalise a set of rules and procedures to navigate this network of courts to maximise its legitimacy, efficiency, and effectiveness.

      • Megan M says:

        Dear JP, thank you for your response, and for your recommendation of this book published by the OPCW. The excerpt that you quoted was very interesting. It highlights the fact that different areas of international law are not watertight compartments, and the issues that may arise when these areas of the law overlap.

        The book that you recommended appears to deal with criminal law, which attributes responsibility to individual actors on an international scale. However, the law of the sea (primarily UNCLOS) and the CWC deal with state responsibility, rather than individual responsibility.

        Therefore, in theory, even if a state were able to escape international responsibility for the use of chemical weapons at sea due to the CWC’s vague reference to the concept of ‘law enforcement’, the individuals involved may be held accountable under international criminal law. However, due to political pressure and the perceived severity of the threat of piracy today, I doubt that neither individual nor state actors will be held accountable in practice.

  4. bucherli says:

    In your original blog post you asked, why the provisions of the CWC should supersede those of the BTWC.

    As far as I understand no provision in the BTWC directly regulates the use of toxin weapons. The BTWC prohibits the development, production and stockpiling of such weapons but not the use per se.

    Thus, the question, whether “law enforcement” can be considered to be one of the “other peaceful purposes”, wouldn’t not come up with regard to the use of the weapon.

    According to customary international humanitarian law, which is binding on all States and on all parties to an armed conflict, the use of biological and chemical weapons is prohibited ( However, the use of such toxin weapons against pirates will hardly constitute an armed conflict nor display itself in the context of an armed conflict.

    Consequently, I assume that the use of toxins as you described here ie. not in the context of an armed conflict has to be assessed from a legal point of view solely in accordance with the CWC and not with the BTWC.

    However, the production of such weapons would fall under the scope of application of the BTWC. One of the “other peaceful purposes” according to Art. 1 (1) BTWC should then, in my opinion, be understood broadly and presumably in view of International Humanitarian Law.

    “Peaceful purposes” as opposite to “(in preparation) of an armed conflict” certainly includes “law enforcement” then. This line of argument relies on the fact, that treaties (normally) bind only states among each other and the nature of protecting commercial vessels is (arguably) part of sovereign police authority rather than a military.

    • JP Zanders says:

      This an interesting take on the matter. Thank you for your argument.

      Two points to consider, however:

      1. At the 4th Review Conference (1996), Parties to the BTWC clarified their understanding of Article I as follows:

      The Conference solemnly recalls the undertaking in Article I never in any circumstance to develop, produce, stockpile or otherwise acquire or retain weapons, equipment or means of delivery designed to use such agents or toxins for hostile purposes or in armed conflict, in order to exclude completely and forever the possibility of their use.

      The key term that requires clarification is therefore not ‘armed conflict’, but ‘hostile purposes’.

      2. Just like the CWC, the BTWC’s ambition is to exclude completely and forever the possibility of their use. In other words, the prohibition is the default position. The CWC makes an explicit exception for law enforcement; the BTWC does not.

      My gut feeling is that since the negotiation of the BTWC there has been an expansion of use of irritants as a law enforcement tool from toxic chemicals to certain irritating toxins based on an understanding of application of non-lethal force. The CWC, with its exception for law enforcement, puts the issue into sharp relief, but nobody seems to have thought of reinterpreting Article I of the BTWC. People who have concerns about toxin use (in general) have tended to turn to the CWC because of the application of the verification regime to toxins (some of which are also listed in Schedule 1).

      I do not recall having come across any statement (at least not with reference to the BTWC) where a state claims exception for the use of toxins for law enforcement purposes. So, since the CWC does not supercede the BTWC, my question (and this is what it is) to the legal community remains open.

      • bucherli says:

        Thank you very much for your reply.

        1. I agree with you, that “hostile purposes” must be broader than “armed conflict”.
        However, I would still argue, that from a strictly legal point of view, hostile purposes stops where they cannot be seen as “military” anymore but revolve around the objects of protection that belong to the competence of police power. It is certainly difficult to draw the line and in many instances unclear. It must be noted, that “competence of police power” does not have to be performed by the police. The fact that the military is protecting objects of protection that belong to the competence of police power does not change the nature of the act.

        The word pair “hostile purposes” appears in other international treaties, e.g. the Environmental Modification Convention. It has always a “military” connotation (e.g. Additional Protocol I, Article 60 and other IHL treaties) and seems to appear oftentimes in combination with the words “armed conflict”.

        Logically, simple “law enforcement” would not fall within the scope of “hostile purposes”, since “law enforcement” does not serve a “military” purpose. The question ultimately revolves around the difficulty in qualifying such counter-piracy acts. My intuition tells me, that they are in the legitimate scope of “law enforcement”. Protecting merchants is whether a military nor a hostile act.

        However, to back up your comment on my post, there are academic scholars, not lawyers though, that seem to support your argument. See for example Dr. Wheelis in Biotechnology and Biochemical Weapons:

        “The BWC prohibits the possession of devices designed to employ biological agents “for hostile purposes or in armed combat.” It thus contains a more expansive prohibition than the CWC—hostile purpose is clearly a broader category than armed conflict, which is, in turn, broader than war. Furthermore, there are no exclusions in the BWC for riot control or for other law enforcement purposes. For these reasons, it would appear that the agents outlined here would be categorically prohibited by the BWC.” (

      • bucherli says:

        My answer on your point 2 is somehow related to the answer I gave in point 1:

        2. The BTWC was signed in 1972 ie. in times where individuals were certainly perceived to a lesser degree as an addressee of an international treaty. The CWC was signed 21 years later. The international community changed considerably in between and you have to take account those historical components when looking at the mere wording of those treaties.

        You cannot put them next to each other and compare them just like that. Thus, in my opinion, the CWC legislates something that is not included in the BTWC ie. the question of international use against non-state actors. This rule could as well be considered potentially as new customs with regards to biological weapons (Art. 31 (3) Vienna Convention on the law of treaties).

        Treaties in Public International Law are primarily interpreted in accordance with the wording. That is certainly due to the fact, that there exists less judicial control in public international law.

        However, treaty content can evolve over time through customs. The Statute of the International Court of Justice acknowledges the existence of customary international law in Art. 38 (1) (b). There is no hierarchy – treaty and customary international law are equally important and the widely acknowledged rules of conflict lex specialis and lex posterior are helpful to solve conflicts.

        Thus, it is, in my opinion, ultimately not a question whether the CWC supersedes the BTWC. The BTWC and the CWC might as well have converged over time.

  5. […] of safeguarding ships threatened by pirates. Some comments to the blog contribution (posted to Arms Control Law) pointed out that under different international treaties, including the Law of the Sea, authority […]

  6. […] of safeguarding ships threatened by pirates. Some comments to the blog contribution (posted to Arms Control Law) pointed out that under different international treaties, including the Law of the Sea, authority […]

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