Relational models of procedural justice propose that fair procedures from authorities communicate that one is an affirmed member of the society that they represent. Authorities who use principles of procedural justice are more likely to be seen as legitimate, increasing compliance and cooperation from the public. However, ensuring that authority decisions will be accepted is not necessarily a guaranteed outcome of employing fair procedures. The empirical evidence discussed here questions what drives perceptions of authority fairness and decision acceptance by considering how social identities shape fairness perceptions. We argue that understanding these processes is crucial for authorities dealing with complex intergroup-level mediations. We support these claims by presenting an experimental study conducted in the context of post-conflict relations between Catholics and Protestants in Northern Ireland. We show that people with more negative outgroup attitudes saw restrictive police actions as fairer when these actions targeted the outgroup (versus ingroup), and more strongly preferred for facilitative police decisions concerning the ingroup (versus outgroup). In contrast, people with positive outgroup attitudes did not evaluate police decisions depending on their own community belonging. The findings suggest that the nature of intergroup relations is a relevant element in responses to authority decisions. We outline new directions to theoretical developments of how authorities can effectively serve social systems that they represent.