In this book, our primary goal has been to trace out a theory of international obligation that makes sense of the contemporary practice of international law, and distinguishes between legal and other social norms. In this conclusion, we will re-state the core conceptual arguments, drawing upon the three case studies, of climate change, torture and the use of force, to illustrate how the elements of our interactional framework play out in practice. We close with a summary of the main implications that the interactional theory holds for international law-makers.

Shared understandings

Social norms can only emerge when they are rooted in an underlying set of shared understandings supporting first the need for normativity, and then particular norms intended to shape behaviour. In the climate context, for example, the growing consensus about the human origins of climate change has anchored the realization that a global legal regime is required. Specific norms also evolve over time, as shared understandings are built up or shifted. Consider the continuing efforts to flesh out the meaning of ‘common but differentiated responsibilities’. It is not enough to look only at the surface of the norm as stated in a formal source, but we must examine with care the underlying shared ground, as well as contested meanings. A detailed example was provided in the discussion of common but differentiated obligations, but the same process can be observed in the definitional arguments over what constitutes torture, and what is meant by self defence.