The strikes conducted this week against Syrian government targets by the US, UK and France are as manifestly illegal as the strikes conducted by the US alone last year. With one exception, the strikes are identical in the arguments made by the intervenors, in the reactions to those arguments by other states, in the deliberate use of silence and ambiguity, and in the consequent inability of this breach of international law to actually cause a shift in international law.
Like last year, the US (and France) failed to put forward any legal argument as to the source of their authority to act under the UN Charter system of the prohibition on the use of force. Their leaders spoke of the imperative need to avoid normalizing the use of chemical weapons; President Trump stated that the purpose of the strikes ‘is to establish a strong deterrent against the production, spread, and use of chemical weapons;’ Prime Minister May said that there was ‘no practicable alternative to the use of force to degrade and deter the use of chemical weapons by the Syrian Regime;’ President Macron spoke of the operation being directed solely against the clandestine chemical arsenal of the Syrian regime.
The language of deterrence used has the flavour of armed reprisals. Not only are such reprisals widely regarded as unlawful, but none of these governments actually clearly sets out an argument on the basis of reprisals. As the ICJ has explained in Nicaragua, para. 207, it is for states to articulate their own legal views, and it is on the basis of these views that other states can react, perhaps towards the creation of a novel rule or exception to an existing rule. In the absence of such a position, however, the approval of the strikes or lack of condemnation by third states has no bearing on the formation of customary international law, or on the evolving interpretation of the Charter. This is the barest minimum of formality required in a legal system, even a flexible one. This is not, as Monica argues in her post, a ‘simplistic’ position lacking in nuance – even if it is conceptually simple, and should be conceptually simple. This is the only dividing line we can have between law and politics, between legal and political arguments.