The 1990s have seen intense debates about the role of regions in European integration. Changes in EU structural funding rules, the innovations of the Maastricht treaty, and the growing importance of federal and regional government within EU member states have all boosted the significance of regional tiers of government in EU politics. Taken together their effect has been to shift the balance of decision-making responsibility within the EU to a third (regional) level of government emerging in the EU policy process alongside the first (union) and second (nation-state) levels. As a result, a system of multi-level governance can increasingly be identified, in which different levels of government adopt different roles in different fields or phases of the European policy process.