The Chemical Line: Rethinking Riot Control Agents in Conflict

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Riot Control Agents (RCAs) are chemical substances, often lacrimators, used during violent outbreaks to temporarily incapacitate individuals without causing long-term harm. These include chemicals such as 2-Chloroacetophenone (CN), o-chlorobenzylidene malonitrile (CS), and oleoresin capsicum (OC), which, to varying degrees, are commonly found in Mace, pepper spray, and tear gas. Most lacrimators have low water solubility and need to be neutralised by being dissolved in a hydrocarbon organic solvent. RCAs are widely used by police forces worldwide for crowd control and riot suppression. 

Under international guidelines, RCAs are treated differently depending on the context in which they are used. The use of RCAs is generally permitted in domestic policing and riot control, but is banned in armed conflict and warfare under international doctrines and domestic regulations. Instruments such as the United Nations Basic Principles on the Use of Force and Firearms by Law Enforcement Officials (1990) allow for the proportionate use of force, including RCAs, to maintain public safety. However, conventions such as the Chemical Weapons Convention (CWC) prohibit the use of RCAs in warfare.

This legal divide has created a grey area in domestic terrorism and internal armed conflict, where operations may simultaneously fall under both law enforcement and military paradigms. This ambiguity is visible in the global outrage against Russia for allegedly using RCAs in Ukrainian regions during the ongoing war. This grey area is also exploited by many countries that use RCAs and other non-lethal chemicals during wartime, citing them as domestic disturbances or methods of civilian control. 

Most urgently, the Organisation for the Prohibition of Chemical Weapons (OPCW) must clearly define the permissible contexts for RCA use and prohibit their deployment against civilians in occupied regions.

Two incidents that display such grey-area scenarios include the May 2005 Blackwater incident in Iraq and the 2018 Mako Brimob Prison Riots in Indonesia. In the Blackwater incident, a private security contractor, Blackwater Worldwide, used a canister of tear gas at a checkpoint, exposing both Iraqi civilians and American soldiers, who suffered respiratory distress and eye irritation. Though CS requires approval from appropriate oversight authorities, the can was used without approval, with the company claiming the use was accidental. 

In May 2018, a three-day prison riot occurred between the Indonesian National Police and those imprisoned at the Mako Brimob prison in Depok, West Java. The inmates took control of one prison block, taking six police officers hostage. The riots ended with the use of tear gas to subdue the prison rioters. 

The impact of RCAs, especially if used incorrectly, can result in long-term respiratory issues, gastrointestinal complications, and vision problems.

In both these cases, the use of tear gas was not to control violent civilian outbreaks, but occurred in grey areas that included the authorities’ attempt to control population unrest. Domestic terrorism and regional conflicts, therefore, present an additional challenge for law enforcement and the military alike. Groups involved in violent acts may not resemble traditional armies but may still require similar strategies. However, it is imperative to ask whether the use of RCAs in domestic riot control or counterterrorism operations is legitimate or whether it potentially violates the spirit of international law. In this regard, the International Committee of the Red Cross (ICRC) has also warned that employing RCAs in situations resembling armed conflict risks undermining the consensus against chemical weapons usage by normalising chemical agent use on the battlefield.

Violations of International Law

Historically, RCAs were seen as practical tools for temporarily incapacitating suspects or dispersing violent crowds. However, more recent studies have shown that the impact of RCAs, especially if used incorrectly, can result in long-term respiratory issues, gastrointestinal complications, and vision problems. In large quantities, they can also act as incendiary agents. The use of RCAs is becoming ever more controversial. Despite this, violations of international law involving RCAs have been reported in various countries and conflict regions. The examples of alleged RCA use by Russia and Israel are listed below.

1. Russia:

Russia has a long history of deploying RCAs in domestic policing, but its use in contested and conflict-prone regions, especially during hybrid warfare, has drawn international scrutiny.

In domestic policing, notably, tear gas was used during the 2011–2013 protests against electoral fraud. In Ukraine, Russia also used tear gas on peaceful protesters in April 2022. Acts like these blur the line between law enforcement and warfare. One of the most contentious examples remains the use of an unidentified chemical agent containing carfentanil—an opioid stronger than fentanyl and listed under the CWC—by Russian forces during the 2002 Moscow theatre hostage crisis, which resulted in the deaths of over 100 hostages. This event also highlights how the unchecked use of chemicals, even when the intention is to incapacitate, can resemble the use of chemical weapons, causing long-term harm and even death. 

2. Israel:

Israel, too, frequently uses RCAs against Palestinian civilians. Tear gas, skunk water, and white phosphorus, are routinely deployed by the Israel Defense Forces (IDF) and the border police against civilians. These actions have been widely criticised and further demonstrate how the use of RCAs and chemicals like white phosphorus—which are not classified as chemical weapons—can still be used in warfare, especially against civilians, under the guise of dispersing hostile crowds, thereby becoming a tool of political and military coercion.   

RCAs, even when used in legally sanctioned scenarios, have ethical drawbacks, including unpredictable effects depending on the environment, and long-term health consequences that are only now beginning to be studied.

Legal and Strategic Recommendations

The instances in Indonesia, Iraq, Ukraine, and Gaza underscore the importance of transparency and military as well as government accountability. If states, unencumbered by international accountability, continue to use RCAs aggressively in situations resembling warfare, it could erode the consensus that ensures chemical weapons remain banned. 

RCAs, even when used in legally sanctioned scenarios, have ethical drawbacks, including unpredictable effects depending on the environment, and long-term health consequences that are only now beginning to be studied. To address the contentious nature of RCAs:

1. Most urgently, the Organisation for the Prohibition of Chemical Weapons (OPCW) must clearly define the permissible contexts for RCA use and prohibit their deployment against civilians in occupied regions. This would help prevent the blurring of military and law enforcement mandates.

2. It is imperative to ensure government transparency. In cases of use, governments must issue warnings to civilians and disclose the chemical composition of RCAs to medical authorities immediately, to avoid tragedies like the Moscow Theatre Hostage Crisis. In the same vein, RCAs should never be used in enclosed environments, where the risk of fatal suffocation is high.

3. As an alternative to RCA's, investment should be directed towards non-lethal technologies—such as directed-energy weapons—that target weapons and machinery without harming humans.

4. Governments should develop clear operational guidelines for RCA use in hybrid operations, including joint police-military actions, ensuring compliance with both domestic laws and international treaties. Further, the OPCW and the United Nations (UN) should provide explicit guidance on RCA deployment in internal armed conflicts or counterterrorism scenarios that fall outside traditional definitions of warfare, with the long-term goal of banning such chemicals entirely. 

Conclusion

The legitimacy of Riot Control Agents in the context of domestic terrorism and warfare remains a contentious issue. While they may offer a less-lethal option in high-stakes environments, their impact is more harmful than previously understood, and their use in grey zones of conflict has led to ethical concerns and a lack of international accountability. With emerging non-lethal technologies that can help better manage violent outbreaks, it is now time to retire RCAs—not just for humanitarian reasons, but also to ensure that the CWC is upheld in both letter and spirit.

Shravishtha Ajaykumar is an Associate Fellow at the Centre for Security, Strategy, and Technology at the Observer Research Foundation.

• International Affairs
• America
• blackwater incident
• mako brimob prison riots
• riot control agents
• riot control agents legitimacy
• riot control chemical
• riot control chemical agents

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