International Relations theory has dealt extensively with norms and agency in normative environments, including the impact of norms on state behaviour; their diffusion and localisation; and their evolution, contestation, and change. Yet, to date the issue of norm conflict has remained theoretically and empirically understudied in International Relations. We still have little understanding of the judgements that governments or institutions make regarding compliance when the directives inherent in the norms to which they have committed appear to be mutually exclusive. The objective of this chapter is to conceptualise norm conflict as a challenge to decision-making in normative international environments and to outline a theoretical framework for studying and understanding norm conflict, including – most importantly – the ways in which states and international institutions seek to resolve it. In so doing, we draw from International Law and Sociology, two disciplines that have extensively dealt with norm conflict.

This chapter reassesses how norm studies around the three moves have advanced and limited our understanding of ambiguous and conflictive relations between norms. It focuses on a specific type of norm relation, a norm collision. Conflicting or incompatible social expectations regarding the appropriate behaviour of actors in a given situation characterise a norm collision. Adherence to one norm may then result in the breach of another. First, the chapter engages with the neglect or limited perspective of norm collisions in the three moves of norm research. Second, it illustrates how choosing a specific norm concept – as connected to each of the three ‘moves’ in norm research – matters for theorising and identifying norm collisions in and between dense and complex institutional frameworks and as a result of contestation. Third, it discusses how crises nurture norm collisions by destabilising agreed-upon norm balances. It uses the most recent transnational and domestic policy responses to the outbreak of the COVID-19 pandemic as an example of how norms interact in practice and how a prioritisation of one norm may (negatively) affect another.

Chapter 3 addresses the potential for norm conflict arising from the parallel application of investment treaties and international humanitarian law. It argues that such conflict must be avoided through treaty interpretation. Drawing from their interaction with human rights law, the rules of armed conflict should inform the meaning of investment treaty clauses through ‘systemic integration’. The chapter shows that investment tribunals possess the authority and duty to conduct such a subordinate examination under humanitarian law as part of the interpretive exercise. Although standards of protection may, as a result, be lower than in peacetime, the chapter argues that giving effect to humanitarian rules through investment law ensures the normative appeal of investment treaties. It allows taking into account military concerns and rejects special treatment of foreign investors compared to ‘ordinary’ civilians. At the same time, the chapter highlights, investment treaties give investors a unique opportunity to enforce international rules during armed conflict and secure compensation for unlawful conduct in hostilities.

Chapter 5 commences the book’s analysis of the operation of the most important investment treaty standards in armed conflict. It focuses on so-called war or armed conflict clauses. These provisions, present in many investment agreements, establish state obligations vis-à-vis investors who have suffered losses during armed conflict and other emergencies. Considering recent arbitral practice in the context of the so-called Arab Spring, the chapter gives guidance on how to understand these understudied clauses, their specific elements as well as their systematic function. While ‘basic’ armed conflict clauses establish a duty of non-discrimination in case the host state compensates other investors for losses suffered, ‘extended’ clauses give a standalone right to claim compensation for certain losses. These clauses convey such a right, among others, in case of requisitioning or unnecessary destruction at the hands of the state’s authorities or armed forces. The chapter shows how the general rules of attribution as well as the rules of international humanitarian law should crucially inform the application of these extended armed conflict clauses.

International trade law is particularly prone to tensions with other areas of global governance given how trade rules interact with public policies addressing environmental and social problems linked to expanding economic activities. This chapter explores how the relations between international trade law and international environmental norms are construed as a matter of law, for example through in-text references to external norms in World Trade Organization (WTO) treaties, and as a matter of social practice, for example when parties make claims about norm relations in the context of WTO litigation, which can catalyse further norm contestation in other ‘fora’. Tracing these legal developments reveals how the international legal landscape can shift due to frictions between bodies of norms. More often than not, such shifts result in subtle adjustments of the relationships between bodies of norms in tension, leaving the substance of overlapping norms unchanged. In some instances, new norms emerge to regulate these interfaces, giving substance to actors’ expectations of how international trade rules should relate to other norms. In this authority game, advantageously negotiating interfaces between bodies of norms becomes increasingly important. The WTO has played this game rather successfully – to the frustration of environmentalists – by establishing strategic linkages on its own terms.

Chapter 5 summarises the inevitable conflict thesis, a major theory on the contemporary significance of military necessity. It becomes necessary for proponents of this thesis to establish that both military necessity and humanity demand some acts and condemn the others. They endeavour to show how, with respect to any given belligerent act, the framers choose to let humanity trump military necessity, let military necessity trump humanity, or find some middle ground between them, and posit an IHL rule accordingly. They insist that every IHL rule embodies this compromise and that neither military necessity nor humanity pleas are consequently admissible vis-à-vis unqualified rules.