The use of chemical weapons, a war crime in the eyes of International Law

The potential use of chemical weapons in the context of the war in Ukraine has once again put on the table a theoretical red line that, in the eyes of International Law, is a war crime. The Organization for the Prohibition of Chemical Weapons (OPAQ) confirmed the use of this weapon in the conflict in Syria, where Russia participates militarily on the side of the Bashar al Assad regime.

The Syrian case once again highlighted the need to eradicate once and for all a type of weapon whose use is particularly indiscriminate. Hundreds of people would have died from toxins such as sarin gas or chlorine in Syria, the result of attacks that Al Assad has always denied.

The specter of chemical weapons has returned to the forefront due to the fear that they will re-emerge in the Ukrainian context. Western governments such as the United States and even NATO have openly warned that Russia may be preparing to use these toxics, perhaps after a ‘false flag’ operation as a pretext.

The OPCW, Nobel Peace Prize winner in 2013 largely for its involvement in the alleged destruction of chemical weapons in the hands of the Syrian regime, is the main international organization in this field; responsible for monitoring compliance with the Chemical Weapons Convention, an agreement that entered into force in 1997 and has been signed by 193 countries, including Russia.

The Rome Statute, the founding treaty of the International Criminal Court (ICC), stipulates that the use of chemical and biological weapons is a war crime, so that their use would be prosecuted before the court in The Hague.

The Prosecutor’s Office of this court has opened a preliminary investigation to determine if war crimes are being committed in Ukraine, an accusation that the Ukrainian and Russian authorities have already crossed. More than 40 countries, including Spain, have claimed these investigations.


The OPCW bases a large part of its work on preventing the use of chemical weapons, but its statutes also open the door to respond in the event that any actor takes a theoretically prohibited step. Thus, it can both provide emergency assistance and open a formal investigation.

Since 2018, and after the evidence on the repeated use of toxic gases in Syria, the OPCW has more room for action, since it can not only confirm or not the use of weapons but point out the guilty. Russia already voted against it, alleging that it represented a political manipulation of the mandate of this agency.

The OPCW, which to questions from Europa Press has preferred not to “speculate” on Western suspicions about Russian plans for Ukraine, can act if necessary if a Member State requires its assistance, in case it is threatened by another country or already have indications that chemical weapons have been used.

The investigation, which can take time, requires field visits and interviews with survivors, witnesses and medical personnel. In the case of Syria, a specific mission was established directly in charge of examining the complaints that were arriving, according to the OPCW with a technical and not a political nature.

The general director of the organization, the Spanish Fernando Arias, recalled this week that chemical weapons are prohibited, “regardless of the circumstances”, on the occasion of the anniversary of the Halabja attack, which massacred some 5,000 people in Iraq in 1988 during the war with Iran.

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The use of chemical weapons, a war crime in the eyes of International Law