Theories of international legitimacy are traditionally based on an international perspective. They assume states as the main actors in the global sphere and consider legitimacy as deriving from state consent. This way of looking at supra-national phenomena has developed together with the formation and the expansion of the (European) international society. It mirrors the epistemological, legal and political framework typical of this society. For this reason, I contend, it is an interpretation biased by a Western-centric prejudice, and alone it is not apt any more to adequately interpret, assess and respond to global challenges. As complementary to the inter-national perspective I suggest to adopt the transcivilisational perspective worked out by Yasuaki Onuma. Such perspective assumes as relevant actors in the global sphere a plurality of civilizations that have long existed in human history. From this perspective, global actions, in order to be legitimate, should mirror values and practices shared by all affected civilisations. This has important consequences for evaluating the legitimacy of international institutions, as I argue by considering the example of the International Criminal Court (ICC). On the one hand, a pure international perspective shows that more than half of the existing states have ratified its statute, thus giving him a rather high level of legitimacy. On the other hand, a transciviliational perspective adds critical insights to such a conclusion. It stresses, for instance, that civilisational differences are fundamental for shaping the lines of consent towards the ICC. I conclude by sketching guidelines for more legitimate international institutions from a transcivilisational perspective.
