This chapter critically discusses the proceduralisation of due diligence obligations. The chapter defines proceduralisation as a process gradually eroding the ‘reasonable’ standard traditionally linked to due diligence and substituting it with specific legal parameters. Through proceduralisation, the content of due diligence obligations is ‘spelled out’ into a series of sub-duties, tecnical standards and direct obligations (including procedural ones) whose fulfilment is required for assessing compliance with the standard of due diligece of the ‘principal’ obligation. The first part of this chapter critically explores this phenomenon, arguing that proceduralisation through interpretative practice raises challenges and comes close to creating new legal rules. The second part illustrates proceduralisation through two case studies taken from international environmental protection and due diligence obligations in international human rights law. The chapter argues that the proceduralisation of due diligence obligations fundamentally tests their dogmatic structure by affecting their nature and content.

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.

This chapter analyses how an international wrongful act accrues from the violation of a due diligence obligation and its consequences. The first part discusses due diligence obligations against secondary rules of ARSIWA concerning the existence of a wrongful act. It is argued that violations of due diligence obligations stem from omissions and that the difficulty of establishing responsibility for failure of due diligence typically concerns the application of rules governing the breach, rather than rules of attribution of conduct. Accordingly, a critical reappraisal of the genealogy of Article 14(3) of ARSIWA and breaches of preventive obligations is undertaken; the chapter argues that the ILC wrongly conceptualised the ‘event’ to be prevented as a secondary rule, this way confusing the relationship between prevention and due diligence. The rest of the chapter examines due diligence obligations against other relevant secondary rules, such as circumstances precluding wrongfulness (specifically, force majeure and distress), the relationship between due diligence and complicity, and how reparation is to be accorded following a breach of due diligence obligations.

Due diligence has increasingly attracted the attention of scholars but it remains an elusive concept. This chapter explains why a study on the dogmatic foundations of due diligence obligations is timely. Thechapter argues that studies addressing the theory of public international law obligations are still scarce. Yet, they are crucial for properly understanding the externalities of obligations and their functioning on the international legal order. Starting with this premise, the chapter asserts that a theoretical study on due diligence obligations serves two main purposes. First, it allows to better clarify the nature, the content and the scope of operation of these obligations, which are traditionally considered difficult to pin down in the abstract. Second, the chapter advances the hypothesis, to be tested in the course of the book, that a dogmatic reconstruction of due diligence obligations also serves normative purposes. The introduction then sets the methodology and scope of the book and explains why the study of due diligence obligations will be limited to obligations of states and will not cover due diligence obligations of international organisations and non-state actors.

This chapter explores the foundations of due diligence under international law. Due diligence emerged in the international practice of the nineteenth century concerning diplomatic protection and the security of states, and developed as a notion linked to the responsibility of states in connection with acts of private individuals. For a long time, due diligence was conceived as a concept pertaining to the realm of international responsibility and it was primarily associated with the measure of a state organ’s fault. The chapter illustrates how, during the twentieth century, due diligence migrated from the realm of secondary rules to primary rules. The chapter clarifies the relationship between due diligence and overlapping concepts, like international liability and the notion of general principles of international law. It is argued that due diligence should be construed as an identifier for a typology of international obligations, something that provides meaning and rationale to them. The chapter concludes by clarifying the difference between due diligence as a ‘qualifier’ for primary rules of states, and due diligence as a ‘process’ linked to the activities of non-state actors.

The conclusion of the book briefly reappraises the main findings of the previous chapters. It argues that a study of the foundations of due diligence from the dogmatic perspective of obligations serves both a cognitive and a normative function. First, the conclusion argues that the theoretical reconstruction of due diligence undertaken by the book has helped to overcome their elusiveness and to better understand the nature of due diligence obligations and how they are operationalised in practice. Second, the conclusion argues that construing due diligence as an identifier for a certain class of primary rules supplies a normative function, as it allows normative considerations to be made about how state responsibility for the violation of these rules accrues.

This chapter explores how due diligence obligations operate in pratice and how their content is determined. The first part explores the factual conditions affecting the scope of a state’s duty to act with due diligence, which are identified in power over the source of risk and knowledge of the risk. The chapter critically discusses the concept of power of the source of risk linked to due diligence and explains the difference between this power and similar notions, like control, influence and jurisdiction. The chapter then argues that the other condition shaping the scope of a state’s duty to act with due diligence is knowledge of the risk and links this knowledge to the concept of state fault. The second part of the chapter discusses the legal and factual parameters affecting the content of due diligence obligations. After thoroughly appraising the concept of reasonableness, the set of variables influencing the degree of diligence expected of a state are identified in: the degree of risk linked to the primary rule; the nature and value of the legal interest protected by due diligence; the level of state capabilities; and the level of state control over the source of risk.