When Norms Fail: ISIS deploys chemical weapons in Mosul

The fight against the group that call itself the Islamic State (ISIS) is not known for sharing globally recognized values. Their actions in the past have shown a degree of brutality that has made it a byword for barbarism around the world. The violation of international norms of behavior brings with it harsh criticism, but does it matter if ISIS does not care?

Chemical weapons have been banned by international treaty: the Chemical Weapons Convention (CWC) bans the possession or use of such weapons. The use of chemical weapons is considered a war crime. There are few aspects of the laws of war that are clearer than these prohibitions. In spite of this, the use of chemical weapons has become more frequent in the wars in Iraq and Syria that include ISIS among the combatants.

When Syria used chemical weapons against its civilian population, this was seen as a gross violation of international norms, a violation of international humanitarian law, a war crime, and a sign that the regime was especially desperate to sow fear in its opponents. In spite of this, the Syrian government has suffered no real consequences for its actions, with Russia and Chine vetoing the latest attempt to impose penalties at the United Nations Security Council.

If a nation state can get away with such a gross break from international norms, what about a non-state actor like ISIS. In spite of its grandiose name, ISIS is not a state. It controls territory, but it is not recognized by any other government. As a non-state actor, ISIS cannot sign the CWC. Only states can sign treaties.

Does this mean that ISIS can act with impunity? The answer is: No. Well, maybe.

In international law there is the doctrine of “jus cogens” which is a fancy Latin term for the concept that there are some norms that simply cannot be set aside. These norms are called “peremptory norms” and they apply to everyone, regardless of the circumstances. The prohibition of the use of chemical weapons is not a peremptory norm. Enough countries have agreed to the CWC that it is pretty close, but there is no clear red line that gets crossed in order to be considered a peremptory norm.

Norms are funny things. They depend on the assumed belief that they reflect the right thing to do in the eyes of the community. This is hard to define and it depends on actions, not just on talk. While it was generally thought that chemical weapons use was across the line, the lack of action against Syria seems to suggest that it is not.

ISIS, as a non-state group, is not accepted as a state, but it is a party to a civil war. As such, the laws of war do apply to it. The expectation is that ISIS will follow the rules of war in its conduct of the conflict. But ISIS explicitly rejects these concepts as Western impositions. The deliberate use of a blistering agent (most likely mustard gas, although this has not been proven definitively) against civilian populations violates several areas of war law.

But this is not new. The Syrian government used chemical weapons against its civilian population. ISIS has used chemical weapons in the past against both civilian and military targets.

But does this matter? While the conflict rages, it is hard to tell. The perpetrators are engaged in the conflict and the world community has no stomach for a major intervention. But there will be an “After the War” time when people seek to return to normal. In this time, there will be calls for justice. Then, the world will have another chance to show whether or not the use of chemical weapons against civilian populations rises to the level of jus cogens.



  1. ISIS is a non-state actor dedicated to a radical overthrow of the international system. As such, violating the norms of that system is not a big leap. Does the violation of norms by such a group matter? Or is the measure of commitment to the norms measured in the international community’s response?
  2. Under international law, is it possible to hold a group that has not signed an international treaty accountable for breaking that treaty’s terms? Can an actor be held accountable for breaking rules they did not agree to in an anarchic international system?
  3. Does the failure to hold a state actor (Syria) accountable for chemical weapons use undermine the case for holding a non-state actor (ISIS) accountable for doing the same thing? In international law, how does the distinction between states and non-state actors impact this?