This chapter lays down the foundations for the argument that questions of (non-)performance raised by the practical phenomenon of sharing international obligations can be tackled by a further categorization and systematization of international obligations, since different types of shared obligations can have different legal implications. It starts by introducing the distinction between indivisible and divisible shared obligations, after which the analysis turns to the issue of how to ascertain the nature of shared obligations, as it will not always be apparent at first glance whether a particular shared obligation is to be qualified as indivisible or divisible. It will be discussed how the distinction between positive and negative obligations as well as the distinction between obligations of conduct and result can facilitate the categorization of a particular shared obligation as either divisible or indivisible. The chapter ends with some reflections on the performance of shared obligations, highlighting how both indivisible and divisible shared obligations can have relevant implications for what is expected of duty-bearers (though in different ways), necessitating a more collective approach to performance.

This chapter asks to which international obligations the concept of due diligence applies and argues that clarifying the nature of these obligations is crucial for understanding the type of conduct expected of a state and for making considerations in terms of international responsibility. In order to situate due diligence within the theory of public international law obligations, the chapter begins by critically illustrating the distinction between obligations of conduct and obligations of result and retraces the history of this taxonomy in the ILC work on state responsibility. The chapter then explores the nature of due diligence obligations, arguing that these are obligations of conduct, linked to the concept of risk and characterised by a degree of flexibility. Through a deductive approach, the chapter maps out the array of primary rules that are typically construed as due diligence duties. it is argued that these rules typically include obligations aimed at avoiding a risk from arising (obligations to prevent; obligations to protect); obligations aimed at ensuring the realisation of particular goals; and other primary rules like duties to negotiate or cooperate.

In order to discuss how the rules on state responsibility may be adjusted to better address human rights violations by non-state actors, it is essential to analyze what concrete responsibilities are to be derived from international human rights law. It is against this background that the second chapter starts by reviewing existing human rights typologies and discusses why – even though these typologies foster the understanding of the historical development of human rights and different human rights categories – they do not provide any further insights on the concrete content of human rights obligations and the circumstances under which state responsibility for human rights violations might be triggered. Therefore, the second chapter proposes a different typology of human rights which is oriented toward the concept of state responsibility. It takes a closer look at what precise obligations might be taken from international human rights obligations and how those obligations could be typologized.

In order to narrow down the concrete content of an international due diligence standard, the third chapter starts with a brief historical summary of how due diligence obligations have entered the international stage. It retraces how the standard of due diligence has been developed in early scholarly writings before it was widely applied in the jurisprudence of so-called Claims Commissions in the context of alien protection laws. In spite of this early recognition, several codification attempts yet have failed which is why the standard of due diligence is not entailed in the ILC’s draft articles on state responsibility that mirror the modern status quo of the customary law on state responsibility. In a second step, chapter 3 therefore undertakes an attempt to locate the position of due diligence obligations in the existing law on state responsibility by comparing and contrasting the standard with other concepts of responsibility.