Perilous Paths: Weaponizing Toxic Chemicals for Law Enforcement

March 2016

By Michael Crowley

Protesters at an elementary school in Nairobi flee to a bridge to escape tear gas used by police on January 10, 2015. The protest, which included students from the school, was over a field that the schoolchildren had used as a playground but had been walled off by a developer for construction. (Photo credit: Tony Karumba/AFP/Getty Images)Since its entry into force in 1997, the Chemical Weapons Convention (CWC) and its associated implementing body, the Organisation for the Prohibition of Chemical Weapons (OPCW),1 have become an important mechanism for global action combating the use of chemical weapons against armed forces and civilian populations under any circumstances, as demonstrated in Syria.

To date, the primary focus of the OPCW, which currently has 192 member states, has been the identification and destruction of all existing chemical weapons arsenals and production facilities around the world.

With the anticipated elimination of all declared chemical weapons stockpiles by 2023, the OPCW is now engaged in a difficult and potentially turbulent process of review, planning, and decision-making likely to transform the nature and activities of the organization for decades to come. Although the future priorities of the OPCW have yet to be collectively agreed by its member states, an initial “vision paper” circulated by OPCW Director-General Ahmet Üzümcü in 2015 stated that “the operating environment of the…OPCW will change significantly over the coming decade. To stay relevant, the focus of the Organisation’s activities will progressively have to be shifted from disarmament of chemical weapons to preventing their re-emergence.”2

An essential element in the OPCW’s effort to prevent the re-emergence of chemical weapons will be its responses to complex and evolving challenges concerning the appropriate regulation of toxic chemicals. One such challenge is the continuing rapid developments in and convergence of chemistry, biology, and other relevant scientific disciplines and associated technologies. Another is the potential desire from certain quarters for weapons employing toxic chemicals for use in operations in which civilians and fighters are in close proximity or are intermingled. In such situations, there are concerns that the lines separating law enforcement, counterinsurgency, and low-level conflict may become blurred.3 These issues are exemplified by the ongoing debates within the OPCW regarding appropriate regulation of incapacitating chemical agent weapons and riot control agents (RCAs).

Riot Control Agents

Riot control agents, commonly known as tear gases, are defined by the CWC as “any chemical not listed” in one of three schedules of restricted chemicals that can produce “rapidly in humans sensory irritation or disabling physical effects which disappear within a short time following termination of exposure.”4 Their use as a “method of warfare” is specifically prohibited under the CWC.5 The convention, however, permits the use of such chemicals for “law enforcement including domestic riot control purposes,”6 provided they are used in “types and quantities” consistent with such purposes.7

Because the CWC does not define or clearly demarcate the boundary between warfare and law enforcement, states might develop varying interpretations of the convention’s restrictions in these areas. Although there is currently agreement among the vast majority of CWC states-parties that RCA use in international and noninternational armed conflict is prohibited, one state-party, the United States, has a national policy permitting use of such agents in certain nonoffensive actions in armed conflict zones.8 Furthermore, previous alleged use by the U.S. military to clear caves in Afghanistan9 and by Turkish armed forces against Kurdish fighters10 were never publicly challenged within the OPCW, raising concerns that such practice may be repeated and potentially gain wider acceptance.

There also is cause for concern over the widespread inappropriate use of riot control agents by law enforcement agencies. When utilized in accordance with manufacturers’ instructions and in line with international human rights law and standards, riot control agents can provide an important alternative to other applications of force more likely to result in injury or death, such as firearms. Law enforcement officials throughout the world regularly use them to disperse violent crowds or to subdue dangerous individuals. Yet, they also are open to misuse. A study of reports from the United Nations and regional human rights bodies and international nongovernmental organizations identified human rights violations committed by law enforcement officials utilizing riot control agents in at least 95 countries or territories from 2009 to 2013.11

Police continue to use these agents to restrict, intimidate, or punish those involved in nonviolent dissent the world over, whether it be children at a Kenyan primary school protesting the seizure of their playground in Nairobi,12 pro-democracy activists engaged in mass demonstrations in the center of Hong Kong,13 or Turkish gay rights activists seeking to march through the streets of Istanbul.14 Sometimes, the chemicals have been employed together with firearms, as in the “organized and premeditated” attack by Guinean police, military, and militia on a political rally held in a stadium in Conakry on September 28, 2009, resulting in the deaths of up to 200 people and the rape of dozens of women and girls.15

A recurring concern voiced by human rights monitors and the medical community has been the use of riot control agents in excessive quantities in open air or in confined spaces, including hospitals, prisons, homes, and even automobiles, where the targeted individuals cannot disperse. In such situations, serious injury or death can result from the toxic properties of the chemical agents or from asphyxiation. This is particularly true for the old, young, or sick. In addition to contravening international human rights standards, the use of riot control agents in such excessive amounts appears to breach the CWC restriction on types and quantities.

Regrettably, despite the ongoing widespread and serious misuse of these chemicals by police and security forces, CWC states-parties have not publicly raised any such cases as matters of concern within the OPCW, nor has any OPCW policymaking organ addressed the nature and scope of “law enforcement” under the CWC. 

Increasing Capability

If the OPCW does not take appropriate action, the situation could dramatically worsen as a result of ongoing development, marketing, and subsequent deployment of a range of systems capable of delivering far greater amounts of riot control agent over wider areas or more extended distances than currently possible with standard law enforcement RCA dispersal mechanisms, such as hand-held sprays, grenades, and single-projectile launchers.

In addition to their potential misuse for collective ill treatment or punishment of crowds, such wide-area RCA delivery mechanisms could be employed as force multipliers in conjunction with firearms, making lethal force more deadly on a large scale. Although nominally developed or acquired for law enforcement, they may also be incorporated into military arsenals, potentially resulting in subsequent use in armed conflict. Certain RCA delivery mechanisms, particularly large-caliber mortar or artillery shells, designated as RCA munitions, could also be used to disperse other toxic chemicals such as classic chemical warfare agents. In addition, current weak trade controls in this area could result in acquisition of RCA delivery mechanisms and misuse by nonstate actors, including armed opposition forces, unregulated private military and security companies, criminal groups, or terrorist organizations.

Investigations by the Omega Research Foundation and the Bradford Non-Lethal Weapons Research Project uncovered the marketing of wide-area RCA delivery systems of potential concern.16 Companies in China, France, India, Israel, South Korea, and the United States have developed a variety of multibarrel launchers capable of firing large salvoes of RCA projectiles indiscriminately affecting substantial numbers of people. For example, U.S. manufacturer NonLethal Technologies Inc. currently promotes the IronFist as a “38 mm weapon system with up to 36 barrels…to rapidly deploy a blanket of less lethal munitions into, or over, a hostile crowd.” When loaded with high-capacity 10-inch rounds, each comprising seven mini-grenades containing the riot control agent CS, the IronFist can deliver “over 250 mini-grenades into the crowd within 2 minutes.”17 Related concerns arise from the marketing of automatic grenade launchers such as the 38 mm vehicle-mounted launcher developed by China Ordnance Equipment Research Institute, which is designed to “cope with mass events quickly and effectively” and is capable of firing 200 tear gas grenades per minute from a distance of at least 300 meters.18

 Russian companies in particular reportedly have developed a disturbing range of RCA delivery mechanisms, including 30 mm grenade rounds for automatic launchers, 105 mm rocket-propelled grenades, 82 mm mortar shells weighing 3.5 kilograms and capable of reaching distances of more than 2.6 kilometers, 120 mm munitions weighing 16 kilograms for use in mortars or artillery that could reach up to 6.8 kilometers, munition dispensers carried by helicopters, and even 500-kilogram cluster bombs packed with chemical irritant submunitions designed to be dropped from low-altitude helicopters or aircraft flying up to 12,000 meters above the target. Information on these RCA munitions was last made publicly available in 2009; it is not known whether production continues or stocks remain.19

A contemporary trend has been the development by companies or state research bodies in China, France, Israel, Spain, South Africa, the United Arab Emirates, and the United States of unmanned ground vehicles or drones capable of carrying RCA-spraying devices or RCA projectile launchers. The South African company Desert Wolf currently promotes the Skunk riot control drone. Capable of holding up to 4,000 pepper balls, this drone is equipped with four high-capacity paintball barrels that can cumulatively release “80 Pepper balls per second, stopping any crowd in its tracks.”20 In October 2015, the company director announced development of a modified Skunk copter capable of carrying up to 48 tear gas grenades, supplied by an unnamed South American company, which can be dropped over crowds.21 Interest in acquiring Skunk drones apparently is not restricted to law enforcement bodies, with Desert Wolf claiming in June 2014 to have “received an order for 25 units” for use by “an international mining house,” with additional potential customers including “mines in South Africa…security companies in…and outside South Africa…and a number of other industrial customers.”22

The employment of certain wide-area RCA delivery mechanisms may be justifiable in particular large-scale law enforcement situations provided they comply with the CWC provision on types and quantities and are used in strict conformity with human rights standards. Other forms of wide-area RCA delivery mechanisms that have been developed, such as artillery shells, aerial bombs, large-caliber mortar shells, and cluster munitions, appear to be completely inappropriate for any form of legitimate law enforcement, having possible utility instead in large-scale human rights abuses or armed conflict. They should be considered to be chemical weapons and treated accordingly.

OPCW Response

In recent years, the OPCW, notably its Scientific Advisory Board, finally has begun to examine these issues. In 2012 the board raised its concerns regarding “reports of the commercial availability of munitions apparently designed to deliver large amounts of riot control agents over long distances.”23 To date, however, few states-parties have clarified their national positions in this area.

Police fire tear gas on pro-democracy demonstrators near government headquarters in Hong Kong on September 28, 2014. (Photo credit: Aaron Tam/AFP/Getty Images)

One notable exception has been Turkey. In September 2010, the Omega Research Foundation, the Bradford project, and the South Africa-based Institute for Security Studies uncovered evidence of the promotion by the Turkish state-owned arms manufacturer Makina ve Kimya Endüstrisi Kurumu of its 120 mm mortar round, the CS MKE MOD 251, at the Africa Aerospace and Defence exhibition held in Cape Town, South Africa, in September 2010. This munition weighed 17.34 kilograms, had a maximum range of 8,132 meters, and was filled with CS. In February 2011, Uğur Doğan, the Turkish ambassador to the OPCW, confirmed that such activities were prohibited under the CWC and that this prohibition extended to other “mortar ammunition containing tear gas or any other prohibited substance.” Turkey consequently reported its destruction of all remaining 120 mm CS MKE MOD 251 munitions, together with epoxy models and promotional materials, and took steps to halt the trade, promotion, and brokering of such munitions.24

Turkey’s robust actions in this area provided a powerful precedent for developing common understandings on this issue. Regrettably, the OPCW has not established mechanisms to determine which forms of RCA delivery systems violate the convention or to effectively regulate the trade and use of those that are consistent with the CWC. 

Pharmacological Weapons

Although the use of appropriate types and quantities of riot control agents for law enforcement purposes is permitted under the CWC, certain countries have developed additional weapons employing other distinct toxic chemicals, notably so-called incapacitating chemical agents (ICAs). These weapons, which ostensibly are for law enforcement, skirt or breach the convention’s prohibitions.

At around 5 a.m. on October 26, 2002, Russian Spetsnaz special forces, in their attempt to save 900 hostages held in a Moscow theater by armed Chechen separatists, employed a secret weapon believed to comprise derivatives of the anesthetic opiate fentanyl. Following mass sedation of the occupants, the special forces stormed the theater and shot all the separatists. Although the bulk of the hostages were freed, more than 120 of them were killed by the chemical agent, and many more continue to suffer long-term health problems. To this day, the Russian authorities refuse to publicly disclose the weapon they employed or provide any details of the nature and levels of such weapons they may have developed or stockpiled.25

Although there is no internationally agreed definition of incapacitating chemical agents under the CWC or elsewhere, they can be described as a disparate range of substances including pharmaceutical chemicals, bioregulators, and toxins that are intended to act on the body’s core biochemical and physiological systems to cause prolonged but nonpermanent disability. They include toxic chemicals that act on the central nervous system to produce unconsciousness, sedation, hallucination, incoherence, disorientation, or paralysis. With inappropriate doses, however, death can result. A variety of these agents are legitimately used for medical, veterinary, or other peaceful purposes, but they could potentially be employed as weapons.

Proponents of such weapons have long advocated their development and use in certain extreme law enforcement scenarios, such as the Moscow siege, where there is a need to incapacitate an individual or a group rapidly and completely without causing permanent disability or fatality. The proponents also have raised the possibility of using them as a tool in a variety of military operations, especially in locations where fighters and civilians are in close proximity or intermingled.

Scientific and medical professional associations, arms control organizations, international legal experts, and human rights and humanitarian organizations, as well as a number of states, have criticized research and development of such weapons, contending that their use presents potentially grave dangers to health and well-being. The British Medical Association concluded that “[t]he agent whereby people could be incapacitated without risk of death in a tactical situation does not exist and is unlikely to in the foreseeable future. In such a situation, it is and will continue to be almost impossible to deliver the right agent to the right people in the right dose without exposing the wrong people, or delivering the wrong dose.”26

Disquiet about these weapons is further exacerbated by concern that rapid advances in relevant chemical and life sciences, particularly genomics, synthetic biology, medical pharmacology, and neuroscience, will be harnessed to the development of such weapons. In a 2012 study, the Royal Society gave warning of “active interest in performance degradation applications of neuroscience for both military and law enforcement purposes” and highlighted “indications of interest among a number of States in the development and use of incapacitating chemical agents.”27

A 2014 survey by the Bradford project documented evidence of continued research in relevant fields by Russian scientists. This included computer modeling of the application of “calmatives” against groups of individuals in enclosed spaces and exploration of the interaction of potential incapacitating chemical agents with human receptor sites. The survey also highlighted the possession by China and the previous reported use by Israel of ICA weapons targeting individuals, while states including the Czech Republic, India, Iran, the United Kingdom, and the United States had conducted research since 1997 that was potentially applicable to the study or development of such weapons.28

As toxic chemicals, incapacitating chemical agents clearly come under the scope of the CWC; their use as weapons in armed conflict therefore is prohibited. Yet, there are differing interpretations as to whether such weapons could be used for law enforcement. Regrettably, no policymaking organ of the OPCW has clarified whether these weapons can legitimately be employed for such purposes and, if so, under what circumstances and constraints. CWC states-parties are left to interpret the scope and nature of their obligations in this area, with the danger that a “permissive” interpretation may evolve. Although the UK, the United States, and other countries have now formally declared that they are not developing and do not possess ICA weapons, some states that have conducted research in this area remain silent.

In recent years, there have been concerted attempts by a growing number of states, led by Australia and Switzerland, to encourage the OPCW to resolve the ambiguities concerning the development and use of these weapons. Throughout 2015, Australia, Canada, Germany, Malaysia, New Zealand, Norway, Switzerland, the UK, and the United States raised the issue within the OPCW Executive Council. In the July 2015 meeting of the council, Robert Mikulak, the U.S. ambassador, “encourage[d] all delegations to consider and subscribe to the notion that the development of so-called incapacitation agents for law enforcement purposes is incompatible with the Chemical Weapons Convention and to put their views on the record in the Executive Council.”29

A significant advance came at the conference of states-parties in December 2015 with the issuance by Australia of a paper titled “Aerosolisation of Central Nervous System-Acting Chemicals for Law Enforcement Purposes” co-sponsored by 21 states. The paper called on states-parties to make known their national positions on the use of such chemicals in law enforcement and was intended to promote discussion within the OPCW, focusing on “developing concrete recommendations for how to address [these] chemicals in a way that would significantly advance one of the OPCW’s priorities—preventing the re-emergence of chemical weapons.”30

Momentum is building for action on ICA weapons, with a growing number of states formally forswearing use of these agents for law enforcement purposes and calling for OPCW-wide consultations. On the other hand, states that possess or may wish to possess such weapons have remained largely silent, only occasionally formally intervening in OPCW meetings. From the limited indications given, Russia and perhaps other states may well try to block or limit this process as it moves forward toward resolution.31

Preparing for 2018

Russian special forces carry hostages out of a Moscow theater on October 26, 2002, after using an unidentified chemical to subdue the Chechen separatists who had seized the theater. (Photo credit: Anton Denisov/AFP/Getty Images)

The 2018 CWC Review Conference has a mandate to examine long-term issues of concern and to “take into account any relevant scientific and technological developments.”32 The conference will be a critical opportunity to address regulation of ICA weapons, riot control agents, and related means of delivery. States concerned about these issues need to prepare the ground now for fruitful and informed deliberations by setting out their positions in national statements or reports and facilitating discussion in suitable forums. These forums notably include the Executive Council and the annual conferences of states-parties, as well as relevant regional forums.

As a first step, states should affirm that their current national practice is to restrict the use of toxic chemicals for law enforcement to riot control agents. Where such a restriction does not exist, states should introduce national moratoriums halting the initiation or continuation of development, acquisition, stockpiling, transfer, and use of ICA weapons for law enforcement purposes. Building on such national action, a group of like-minded states could introduce a moratorium on such activities at the plurilateral level.

States also should consider pressing for the establishment of a dedicated, open-ended working group or some other formal mechanism within the OPCW to make recommendations on these issues for consideration by the review conference. In addition to addressing ICA weapons, the working group should seek to clarify the limitations on RCA use for law enforcement, specifically taking into account CWC constraints on types and quantities as well as those arising from international human rights law. The working group also should develop criteria for determining which means of delivering and dispersing toxic chemicals are inappropriate for law enforcement purposes and would consequently breach the convention.

In the coming years, the OPCW is expected to oversee the destruction of the last declared elements of Cold War-era state chemical weapons programs. To remain relevant, the organization must embark on a process of reform and renewal to meet the new security challenges. Critical to the success of this process will be whether and how the CWC states-parties resolve certain controversial issues that they have previously avoided, notably the development and use of weapons employing toxic chemicals for law enforcement purposes. Failure to set clear boundaries in this area risks the introduction and misuse of inappropriate weapons by police, security, and military forces; the danger that such weapons will subsequently be employed for actions beyond law enforcement; and the threat of their proliferation to other state and nonstate actors. In addition to the detrimental consequences for human rights and human security, such developments could undermine the stability of the convention itself.


1.  For an online version of the text of the Chemical Weapons Convention (CWC), see Organisation for the Prohibition of Chemical Weapons (OPCW), “Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on Their Destruction,” n.d.,

2.  OPCW Technical Secretariat, “The OPCW in 2025: Ensuring a World Free of Chemical Weapons,” S/1252/2015, March 6, 2015.

3.  OPCW Technical Secretariat, “Report of the Advisory Panel on Future Priorities of the Organisation for the Prohibition of Chemical Weapons,” S/951/2011, July 25, 2011, para. 13.

4.   CWC, art. II.7.

5.   Ibid., art. I.5.

6.   Ibid., art. II.9

7.   Ibid., art. II.1.a.

8.   Exec. Order No. 11850, 40 Fed. Reg. 16187 (April 8, 1975). See also U.S. Department of Defense,  “Law of War Manual,” June 2015, sec. 6.16,

9.   James D. Fry, “Contextualized Legal Reviews for the Methods and Means of Warfare: Cave Combat and International Humanitarian Law,” Columbia Journal of Transnational Law, Vol. 44, No. 2 (February 2006): 453-519.

10.   Sunshine Project, “A Survey of Biological and Biochemical Weapons Related Research Activities in Turkey,” Sunshine Project Country Study, No. 3 (December 8, 2004), p. 15,

11.   Michael Crowley, Chemical Control: Regulation of Incapacitating Chemical Agent Weapons, Riot Control Agents and Their Means of Delivery (Basingstoke, Hampshire: Palgrave Macmillan, 2016), pp. 50-70.

12.   Jeffrey Gettleman, “Kenya Investigates Use of Tear Gas on Schoolchildren,” The New York Times, January 20, 2015.

13.   BBC News, “Hong Kong: Tear Gas and Clashes at Democracy Protest,” September 28, 2014,

14.   Amnesty International, “Amnesty: Pride March Ban Is a New Low,” June 30, 2015,

15.   After surrounding all exits, police fired tear gas into the stadium, causing fear and confusion among the tens of thousands of peaceful pro-democracy supporters within. The combined forces then entered the stadium, shooting directly at the packed and terrified crowds. According to an International Commission of Inquiry, “[D]ozens of people attempting to escape through the stadium gates either suffocated or were trampled to death in stampedes, which were compounded by the use of tear gas.” Human Rights Watch estimated that 150 to 200 were killed and dozens of women and girls were raped in this attack. UN Security Council, “Letter Dated 18 December 2009 Addressed to the President of the Security Council by the Secretary-General,” S/2009/693, December 18, 2009, annex (containing “Report of the International Commission of Inquiry Mandated to Establish the Facts and Circumstances of the Events of 28 September 2009 in Guinea” at paragraph 198); Human Rights Watch, “Guinea: September 28 Massacre Was Premeditated,” October 27, 2009,

16.   Michael Crowley, “Drawing the Line: Regulation of ‘Wide Area’ Riot Control Agent Delivery Mechanisms Under the Chemical Weapons Convention,” Bradford Non-Lethal Weapons Research Project and Omega Research Foundation, April 2013,; Michael Crowley, “Tear Gassing by Remote Control: The Development and Promotion of Remotely Operated Means of Delivering or Dispersing Riot Control Agents,” Oxford Research Group, December 2015,

17.   NonLethal Technologies Inc., “The IronFist: The Cost Effective Solution for Rapid Deployment of Non-Lethal Munitions,” n.d.,

18.   Crowley, “Tear Gassing by Remote Control,” pp. 10-11 (citing an undated catalog distributed at the Asia Pacific China Police Expo 2012 by the China Ordnance Equipment Research Institute in Beijing on May 22-25, 2012). Information is from an unofficial translation of the Chinese original on file with the Omega Research Foundation.

19.   Crowley, “Drawing the Line,” pp. 25-38.

20.   Desert Wolf, “Skunk Riot Control Copter,” n.d.,

21.   Guy Martin, “Desert Wolf Adding Grenades to Skunk Riot Control UAV,” Defenceweb, October 7, 2015,

22.   Leo Kelion, “African Firm Is Selling Pepper-Spray Bullet Firing Drones,” BBC News, June 18, 2014,

23.   OPCW Conference of the States Parties, “Report of the Scientific Advisory Board on Developments in Science and Technology for the Third Special Session of the Conference of the States Parties to Review the Operation of the Chemical Weapons Convention,” RC-3/DG.1, October 29, 2012.

24.   Crowley, Chemical Control, pp. 102, 232-234.

25.   Ibid., pp. 15-16.

26.   BMA Board of Science, “The Use of Drugs as Weapons: The Concerns and Responsibilities of Healthcare Professionals,” British Medical Association, May 2007,

27.   The Royal Society, “Brain Waves Module 3: Neuroscience, Conflict and Security,” February 2012,

28.   Michael Crowley and Malcolm Dando, “Down the Slippery Slope? A Study of Contemporary Dual-Use Chemical and Life Science Research Potentially Applicable to Incapacitating Chemical Agent Weapons,” Bradford Non-Lethal Weapons Research Project and Biochemical Security 2030 Project, October 2014,

29.   Robert P. Mikulak, Statement to the OPCW Executive Council, July 7, 2015,

30.   OPCW Conference of the States Parties, “Aerosolisation of Central Nervous System-Acting Chemicals for Law Enforcement Purposes,” C-20/NAT.2/Rev.1, December 3, 2015 (joint paper by Australia, Austria, Belgium, Brazil, Bulgaria, Canada, Chile, Cyprus, Germany, Finland, Ireland, Japan, New Zealand, Norway, Poland, Portugal, Korea, Spain, Switzerland, Turkey, the United Kingdom, and the United States).

31.   OPCW Executive Council, “Statement by the Delegation of the Russian Federation at the Seventy-Ninth Session of the Executive Council,” EC-79/NAT.15, July 8, 2015.

32.   CWC, art. VIII.22.

Michael Crowley is project coordinator of the Bradford Non-Lethal Weapons Research Project at Bradford University and is a research associate with the Omega Research Foundation. He has worked for more than 20 years on arms control and human rights issues with organizations such as Amnesty International, the Arias Foundation, the British American Security Information Council, and the Verification Research, Training and Information Centre. Research for this article is drawn in part from his book Chemical Control: Regulation of Incapacitating Chemical Agent Weapons, Riot Control Agents and Their Means of Delivery (2016).