A path already travelled in domestic orders? from fragmentation to constitutionalisation in the global legal order.

Theories of fragmentation and constitutionalisation have long been presented as antagonistic accounts of the global legal order. Fragmentation theorists posit a non-hierarchical order explained in terms of the relationships between general and specialised areas of international law. Constitutionalisation’s adherents, by contrast, identify the global legal order’s ongoing transformation from horizontal and consent-based roots towards a hierarchal structure grounded upon fundamental principles. The proliferation of international tribunals has long been recognised as a factor muddying the picture of constitutionalisation and pointing towards fragmentation within international law. We argue, however, that this proliferation enhances the global order’s potential for constitutionalisation. The current state of fragmentation within the uncodified global order is comparable to long periods when the UK’s uncodified constitution exhibited the hallmarks of fragmented development. We bridge these supposedly rival explanations for the development of legal orders by re-evaluating the role played by competing courts in the UK’s constitutionalisation process, reassessing developments familiar to common-law historians through the prism of fragmentation theory. The UK example indicates that fragmentation is not, of itself, an insurmountable obstacle to constitutionalisation within the global order and may even mark a stage within this process. We employ lessons derived from this comparison to evaluate current flashpoints in relations between international tribunals, including the European Court of Justice’s Opinion 2/13 which has for now stymied the EU’s efforts to accede to the European Convention on Human Rights