Exception to a fair scheme of cooperation? A normative assessment of involuntary exclusions, non-compliance with treaty obligations, and post-differentiation reintegration in the European Union.

The normative literature on differentiated integration (DI) has specified conditions under which DI can be regarded a fair scheme of cooperation. The paper first develops a framework for the assessment of fair international cooperation, building on republican-statist and liberal-cosmopolitan perspectives. Subsequently, the framework is applied to three forms of DI which seemingly contradict fair cooperation: involuntary exclusions from EU policies, non-compliance with treaty obligations to join the common currency, and continued policy alignment despite formal opt-outs. For each form, the paper offers a conceptual clarification and provides an empirical overview before discussing its normative implications. The empirical mapping shows that the three forms of DI are not as exceptional as may have been expected. Each form affects multiple EU member states, often for extended periods of time. Normatively, each of the three forms poses significant challenges to fair cooperation in the EU. Involuntary exclusions are procedurally problematic if accession is vetoed by other member states for reasons different from the initially stipulated technical criteria for inclusion. Non-compliance with treaty obligations represents a challenge to the rule of law in the EU, which neither democratic nor functional arguments can justify. Post-differentiation alignment is especially problematic where legal non-participation is rooted in a democratically expressed popular preference.