Territorial diplomacy is the “small” foreign policy practised by local and regional authorities, who thereby become genuine actors in international relations. It originally began with the policy of Franco-German town-twinning after World War Two for the purpose of reconciliation. Fostered since the 1980s by globalization and the process of European integration, cities, regions, and federal states in Europe have increasingly contributed to the “main” foreign policy conducted by their national governments, as well as to the implementation of European Regional Policy and the European Neighbourhood Policy. Their diplomacy is often informal. However new legal instruments, both European and national, now enable them to formalize their close neighbourly relations. The external action of local and regional authorities has therefore gradually broadened and put an end to the traditional conception of the Westphalian state, which possesses the privilege of exclusivity over foreign policy.
Source : Territorial Diplomacy