|This chapter discusses the role which may be played by legal norms (rules and principles) in seeking to achieve coherence in EU foreign policy. The premise is not that legal norms are the best way (or a better way) to achieve coherence, but rather the intention is to examine the extent to which the Treaties and Court of Justice have developed norms which are relevant to the struggle for coherence and to explore the role they might play, as well as their limits. We need first to explore what coherence means, and whether it is a concept which has any specifically legal content at all (section II). In thinking about coherence, lawyers have often started with the distinction that derives from political science literature between vertical and horizontal coherence. This analysis is also based on that framework, addressing vertical coherence in section III and horizontal coherence in section IV. However, in order to understand the specifically legal dimension of coherence a different conceptualization is superimposed on this basic distinction, which addresses the fact that there are different dimensions to coherence as a concept and that these are regulated by different rules and principles. The conceptualization offered here is of three different levels of coherence: the first is consistency, seen in terms of conflict resolution and requiring rules of hierarchy; the second is the effective allocation of tasks between actors and instruments, avoiding both gaps and problematic duplication and requiring rules of delimitation; the third is synergy between norms, actors and instruments, requiring principles of cooperation and complementarity.