Given the current and concurrent crises of the EU and the Euro, it would seem appropriate to explore the hypotheses and presumptions that neo-functionalism might employ to predict “spill-backs” rather than “spill-overs.” A spill-back is when member states no longer wish to deal with a policy at the supranational level; an example would successive exits from the Eurozone and the EU be they coerced (Grexit) or voluntary (Brexit), and/or the collapse of the Euro. Such “spill-backs” are fervently advocated by parties on the radical left and right (albeit for different reasons) in both debtor and creditor states (e.g. Freiheitliche Partei Österreichs, Front National). When and why should one expect that a given set of institutions of regional integration would agree (or be forced) to withdraw their competence to make policy in an arena previously subject to its trans-national “governance”? Or, more dramatically, under what condition might it collapse altogether?