The Countermeasures of Others: When Can States Collaborate in the Taking of Countermeasures?

Abstract

In the last few years, States have put forward policies and proposals for cooperation in the taking of countermeasures in various fields of international law. In this article, we ask whether, and if so under what conditions States, may lawfully collaborate in the taking of countermeasures against another State. We distinguish five different types of collaboration. These are independent but coordinated action; secondment; joint action; aid and assistance; and what we term ‘proxy countermeasures - the idea of taking a measure at the request and on behalf of another State. We consider the permissibility of the collaborating State's actions in two distinct situations: where this State is itself entitled to resort to countermeasures, and where it is not. In relation to the potential evolution of the law, we draw attention to certain legal and policy considerations, as well as plausible avenues for development.

Keywords: Countermeasures, State Responsibility, Erga Omnes obligations, Collective Countermeasures, Cyber-Countermeasures, Third Parties, Complicity, Aid and Assistance, Joint Responsibility