ABSTRACT
The primary task of Chapter 4 is to demonstrate that obligations (legal duties) are fundamental to the differentiation of international obligations. However, not all typologies of international obligations have the same practical and theoretical value. Nor do they all have sufficient legitimacy. Moreover, the fact that a certain division of obligations is controversial does not mean that it is useless. The chapter considers the impact of the classification of sources, in particular treaties (e.g., law-making and contractual treaties) and norms (e.g., peremptory and dispositive norms) on the classification of international obligations. Additionally, the relevance of the elements of the obligation structure to the creation of different categories of obligations is examined (e.g., the role of subjective element: bilateral and obligations erga omnes; the nature of the behaviour required: reciprocal and non-reciprocal obligations, unilaterally, bilaterally, and multilaterally binding obligations, obligations of results and obligations of conduct/due diligence). Not only the divisions of obligations themselves and their justifications are considered, but also their transformations (such as bilateralisation of multilateral treaties).
