The last two weeks have provided a reminder of the difficulty in formally assigning blame for chemical weapons use in Syria and important steps toward addressing that problem. On Nov. 24, Syrian rebels allegedly used chlorine gas in an attack on regime-controlled parts of Aleppo. Syrian regime and Russian media sources reported the attack, which caused multiple casualties though no deaths. The Syrian Observatory for Human Rights — a more neutral source — also reported that shells fell “in Al-Khalidiya neighborhood and Jam’iyyat Al-Zahraa neighborhood,” causing “suffocation.” Russian government and Syrian regime officials quickly blamed opposition forces for using chemical weapons. Aside from the deep hypocrisy of the Syrian regime — the primary perpetrator of chemical weapons attacks in Syria — condemning the use of chemical weapons by its opponents, the allegations against rebel forces are complicated. On one hand, Daesh has used chemical weapons in Syria, and it is possible that other opposition forces have too. On the other hand, many observers have a complete lack of faith in official Syrian and Russian sources. Several questions have been raised about the Russian and Syrian government reports, including by Syria analyst Charles Lister, who challenged Russian claims about a specific mortar delivering the gas. Some analysts suspected that Syrian regime and Russian forces were seeking an excuse to launch an offensive in the Idlib area, despite the truce agreed between Turkey and Russia in September. Fundamentally, in the middle of a war in which all sides have motivations to falsely accuse their opponents, it is difficult for the international community to verify whether a chemical weapons attack occurred and especially who was responsible. There are several reasons why attribution for chemical weapons is challenging. There are practical obstacles to investigating an attack in a war zone. Experts who might be able to verify an attack and identify the source often cannot move quickly into an unsafe area, or the government or other forces might impede them. If they are delayed in reaching an attack site, evidence might have dissipated or been destroyed. Claims made by a party to the war are always suspect. Attacks that use sophisticated nerve agents, such as sarin, are easier to attribute, since limited actors possess such weapons; in Syria’s case, the regime is very likely to be responsible for any such attack. Attacks using more easily accessible gases, such as chlorine, theoretically could be linked to the regime or opposition forces. Delivery mechanisms also matter. Attacks involving barrel bombs pushed out of helicopters are almost certainly perpetrated by the Syrian regime, while those using more widely available forms of delivery, such as mortars, can be more difficult to attribute. Another challenge is that there are different degrees of certainty in assigning responsibility for an attack. Often, there is substantial evidence based on journalists’ reporting, eyewitness accounts, doctors’ reports and more; some reports, such as by Human Rights Watch, draw on these sources, which can provide a significant body of evidence. However, the standards of experts, UN bodies and governments are often much higher, requiring expert investigators to follow specific protocols. This high bar means that such investigations are extremely well researched and highly reliable, but resources and opportunities for such in-depth investigations are limited and will only apply to a very small number of chemical weapons attacks in a place such as Syria. Attacks that use sophisticated nerve agents, such as sarin, are easier to attribute, since limited actors possess such weapons; in Syria’s case, the regime is very likely to be responsible for any such attack. Kerry Boyd Anderson There are tools available for conducting expert investigations, primarily through the UN and especially through the Organization for the Prohibition of Chemical Weapons (OPCW). The OPCW is responsible for helping states implement the Chemical Weapons Convention (CWC), which bans the possession and use of chemical weapons. Until recently, however, the OPCW had no authority to attribute responsibility for chemical weapons attacks. There was a temporary Joint Investigative Mechanism (JIM) of the UN and OPCW, which had the authority to investigate specific chemical weapons attacks in Syria and determine who had perpetrated them. While the JIM could not investigate all allegations, it formally attributed several chemical weapons attacks to the Syrian regime and two attacks involving sulfur mustard gas to Daesh. In November 2017, Russia vetoed renewing the JIM’s mandate. In response, many countries that were worried about the erosion of the global norm against chemical weapons decided to look for alternative measures. One was the French-initiated International Partnership Against Impunity for the Use of Chemical Weapons, designed to name and shame perpetrators of chemical weapons attacks. Perhaps more significantly, in June, at a special meeting, OPCW member states voted to allow the organization to investigate and attribute responsibility for chemical weapons attacks in Syria. This move gets around Russia’s veto. Importantly, last week, at the Fourth Review Conference of the CWC, the parties chose to include funds for this new work in the OPCW’s budget. Investigators will continue to face many challenges, but there is now a mechanism for independently verifying whether chemical weapons attacks took place and who was responsible. Given that the previous JIM assigned blame to both the Syrian government and Daesh, one might think that Russia and the Syrian regime would support an independent mechanism that could validate their allegations against opposition forces — if, in fact, those claims are true. Any use of chemical weapons is illegal and appalling. These are not battlefield weapons but rather weapons of terror. The international community should condemn all perpetrators — regardless of whether they are governments, terrorist groups or opposition forces. Kerry Boyd Anderson is a writer and political risk consultant with more than 14 years’ experience as a professional analyst of international security issues and Middle East political and business risk. Disclaimer: Views expressed by writers in this section are their own and do not necessarily reflect Arab News" point-of-view