Shared obligations in international law

Throughout the years, international legal society has become increasingly interdependent. States and international organizations (IOs) engage in cooperative activities and pursue common goals that cannot be achieved by any of them independently. In this context of interdependence, cooperation and pursuance of common interests one might expect that states and/or IOs do not only share rights and legal interests (which is generally recognized in international legal literature) but that they may also share international obligations.
In practice, there are various situations in which multiple states and/or IOs are bound to an international obligation in the context of cooperative activities and the pursuance of common goals. Moreover, one may find an increasing number of references to international obligations that are 'shared', 'joint' or 'collective' in legal literature, which suggests that the idea that the fulfilment of international obligations is not always up to one duty-bearer only is gaining support. Nevertheless, there has been no comprehensive attempt to define what it means to speak of shared obligations in international law.
This thesis examines the topic of shared obligations in international law, and answers the following research question: in what situations are international obligations shared rather than individual, and what are the implications of a breach of a shared obligation for the international responsibility of states and/or IOs? The study distinguishes between two types of shared obligations: divisible and indivisible shared obligations. It finds that the relationship between shared obligations and shared responsibility depends on whether the shared obligation breached is divisible or indivisible.