This post is the latest installment of our “Monday Reflections” feature, in which a different Just Security editor examines the big stories from the previous week or looks ahead to key developments on the horizon.

The intertwined conflicts in Syria and Iraq continue to horrify.  The Syrian Commission of Inquiry recently concluded that genocide against the Yezidi is “ongoing” and called for greater protective measures from the international community. War crimes and crimes against humanity continue apace throughout the conflict in Syria, with Aleppo still under an intense siege (see my earlier coverage here).  And now, three years after the international community attempted to rid Syria of the Assad regime’s chemical weapons, the threat of poison weapons remains, as evidenced by last week’s reports of a deadly toxin attack in northern Syria likely involving chlorine gas dropped by helicopter. Although there is no definitive determination of what type of chemical was used or who was responsible, there is speculation that the alleged attack was committed by regime (or maybe Russian) forces in reprisal for the recent downing of a Russian helicopter in the area (which resulted in the biggest single loss of life for Russia in Syria).

Amidst the latest appearance of chemical warfare in Syria, it is worth looking into what international law has to say on the use of such weapons in a situation as complicated as the Syrian civil war. 

The ICC Statute & Its Amendment

Starting with the Statute of the International Criminal Court (ICC): as originally drafted, the war crimes provision specifically penalized the use of certain weapons only in wars between two or more states, known as International Armed Conflicts or IACs. In particular, Article 8 made it criminal to use poison or poisoned weapons, asphyxiating, poisonous or other gases, and all analogous liquids, materials and devices. At the same time that ICC States Parties finalized the definition of the crime of aggression in 2010 at the Kampala Review Conference, however, this IAC weapons ban was extended to cover Non-International Armed Conflicts (NIACs).  The conflict in Syria—involving multiple non-state groups fighting one another and against various states—is a NIAC. Originally proposed by Belgium, this extension (official text is here), garnered the necessary 30 ratifications upon El Salvador’s March 2016 ratification of the ICC treaty along with its two sets of amendments (see the ICRC’s IHL treaty database for the latest).

These amendments to the ICC Statute were billed as a logical extension of a set of prohibitions that already existed in IACs. That said, this seemingly innocuous harmonization of the law across conflicts met some resistance. This reflects the fact that certain chemical agents (and flattening bullets, the subject of another amendment to the ICC Statute) that might meet the technical definition of prohibited weapons under International Humanitarian Law (IHL) remain lawful when used in certain law enforcement situations (such as for riot control and in hostage-rescue operations) as a less lethal alternative to deadly force. There was concern that the disparate legal treatment of this technology under IHL, which governs armed conflict situations as compared to times of peace, may give rise to unfairness or confusion in so-called “three-block wars.”

This latter concept reflects the fact that in contemporary armed conflicts, a state’s armed forces may be involved in full-scale combat on one block, a stabilization operation on the next block, and a humanitarian relief or reconstruction effort on a third block. Using a substance like tear gas for riot control on one block might trigger war crimes liability on the next block if IHL were applicable. States also argued that the penal prohibition in the ICC Statute should not apply to substances with only temporary effects. This “safe haven” is reflected in the ICC’s Elements of Crimes, which contain a harm threshold requiring a showing that the poison or prohibited gas substance “causes death or serious damage to health in the ordinary course of events, through its asphyxiating or toxic properties.”

Other Chemical Weapons Prohibitions Under International Law

In addition to the ICC Statute, there are a number of historical and modern international instruments prohibiting the use of a range of chemical weapons, including the 1899 Hague Declaration Concerning Asphyxiating Gases, the 1907 Hague Declaration on the Laws and Customs of War on Land, the 1925 Geneva Gas Protocol, and the 1993 Convention on the prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on their Destruction (CWC). Chlorine gas was first used in 1915 during World War I as a stratagem against the impasses occasioned by trench warfare.

Syria ratified the CWC in 2013 as part of the U.S.-Russian Joint Framework Agreement on Chemical Weapons. The Framework Agreement was, in turn, blessed by UN Security Council Resolution 2118, which required Syria to dismantle its chemical weapons arsenal under international supervision. None of these treaties, except the CWC, envisions an international penal regime or applies in all conflict circumstances, including NIACs. The Hague Declaration and the Geneva Gas Protocol, for example, ban parties who are fighting each other from using chemical weapons, but do not necessarily apply when parties are engaged in internal armed conflicts or in IACs involving non-party states. All that said, a well-respected study of customary international law by the International Committee of the Red Cross (ICRC) states at Rule 74 that any chemical weapon use is now prohibited in both NIACs and IACs (a conclusion that is not uniformly shared). And, in its resolutions addressed to chemical weapon use in Syria, the Security Council consistently calls for accountability, implying that the use of chemical weapons in a NIAC is a war crime.

It should be noted that chlorine gas—which has a range of benign civilian uses—was not included in the internationally-brokered chemical weapon ban back in 2013, although the Organization for the Prohibition of Chemical Weapons is tracking its use in Syria.  The use of chlorine gas would, however, violate the CWC, which Syria ratified in 2013.  When inhaled and put in contact with moisture, chlorine gas converts to hydrochloric acid, which can lead to internal burning as well as drowning when a person’s lungs release excess water in an effort to neutralize the gas. Although it produces agonizing symptoms, chlorine gas is not as lethal as other chemical weapons, such as sarin gas which has also been used in Syria, starting in Ghouta in August 2013.

Could the ICC Prosecute the Use of Chemical Weapons?

Coming cold to the text of the ICC Statute, one would assume the genus crimes of “employing asphyxiating, poisonous or other gases, and all analogous liquids, materials or devices” would encompass the use of chemical (and maybe some biological) weapons. Knowing the treaty’s drafting history, however, reveals that a provision specifically penalizing the use of “chemical weapons” was deliberately rejected by delegates as part of a compromise around the inclusion of nuclear weapons. States from the developing world wanted a provision criminalizing resort to nuclear weapons; states from the developed world wanted a provision on chemical and biological weapons. This gulf between the poor man’s and the rich man’s weapons of mass destruction has long bedeviled disarmament efforts.

The stalemate was resolved by excluding explicit reference to both categories of weapons and adding a placeholder that might one day allow for their piecemeal inclusion. The ICC Statute at Article 8(2)(b)(xx), governing IACs, thus would allow for the prosecution of individuals shown to have employed, “weapons, projectiles and material and methods of warfare which are of a nature to cause superfluous injury or unnecessary suffering or which are inherently indiscriminate in violation of the international law of armed conflict.” However, this provision will not be activated until “such weapons, projectiles and material and methods of warfare are the subject of a comprehensive prohibition and are included in an annex to this Statute, by an amendment in accordance with the relevant provisions set forth in articles 121 and 123.”

Although Belgium attempted to generate just such a list of munitions in time for the Kampala Review Conference, there was insufficient support at the time and the provision remains a dead letter.

So far, the ICC has only limited jurisdiction over events in Syria (namely, crimes committed by the nationals of ICC states parties).  If eventually confronted with charges involving the use of chemical weapons, the ICC will be obliged to interpret the text of its constitutive document, now amended, in light of this legislative history to determine which charges to allow.

Other Potential Charges

In the absence of a specific chemical weapon prohibition, the use of such inherently imprecise weapons could be charged as an indiscriminate attack or as launching an attack with the purpose of inflicting terror among the civilian population. Likewise, the use of such weapons within urban or densely populated areas could also be charged as an intentional attack on civilians, even if the weapons managed to strike proper military objectives. If the harm to civilians is sufficiently acute, an indiscriminate attack could thus be regarded as the equivalent of a direct attack, and even a crime against humanity. Absent an express weapons ban, the use of chemical weapons against armed actors (vice civilians) may not be prosecutable. Regardless of where prosecutions proceed, the use of all these prohibited and problematic weapons in Syria offers an opportunity to generate modern jurisprudence around such munitions.