Territorial diplomacy is a relatively recent concept in International Relations, emphasizing the external actions of infra-national stakeholders (cities, federal states, local authorities). Since the late 1980s their intervention in international policy alongside other transnational actors such as NGOs or multinational corporations has been facilitated by two major developments: first, the process of globalization, which has contributed to the “decomposition” of the Westphalian state as the sole legitimate international actor for external policy; and secondly, the process of European Integration and the transformation of the European Union (EU) into a sui generis actor, virtually a state, which institutes a multi-level system of governance in which local and regional authorities intervene alongside national governments.
The notion of territorial diplomacy has multiple meanings and includes numerous formulations in scientific literature such as para-diplomacy, sub-state diplomacy, regional diplomacy, city diplomacy, local and regional diplomacy, decentralized diplomacy, etc., which do not necessarily reflect the same approach to external action of infra-national actors.
In France, territorial diplomacy is tightly connected to that of decentralized cooperation, which generally takes the form of the implementation of a local developmental aid policy and the establishment of extra-European intercommunal partnerships (North-South). From this perspective, territorial diplomacy serves as the local extension of the state's foreign policy and is built through cooperation and in complementarity with the latter. The legitimacy of this international action of local authorities has its origins in the practice of town-twinning that was initiated after World War Two between France and Germany with the aim of reconciling the two countries. In the United States, on the other hand, the origin of a municipal foreign policy came from the mobilization of local populations against US foreign policy in the 1980s. They for example boycotted investments in certain countries, which were considered unethical, or they welcomed illegal refugees fleeing conflict in Latin America. This concept of a city diplomacy “independent” of the state was taken up by the United Cities and Local Governments network founded in 2004, which brings together the world's infra-national entities. During a meeting in Marrakesh in 2006, it defined city diplomacy as the “tool of local authorities for the promotion of social cohesion, the prevention of conflicts, and post-conflict reconstruction”.
However, the “European” terminology for territorial diplomacy surpasses the framework of decentralized cooperation or local diplomacy referred to above: firstly, at the European level, it is also understood as a para-diplomatic action on the part of federated states, one that is authorized in federal systems and inscribed as such in their constitutions (for example in Germany or in the Swiss Confederation). Secondly, in the context of European integration and especially after the introduction of the principle of subsidiarity in article 3B of the Maastricht Treaty of 1992, territorial diplomacy also became a tool for local and regional authorities to participate in European policy. They conduct a “minor” foreign policy within the EU, which enables them to go beyond national borders by developing interregional, cross-border, transnational, and macro-regional cooperation. This European territorial diplomacy is firstly supposed to contribute to the implementation of EU Regional Policy. With the creation of the Interreg program by the European Commission in 1990, the European Community directly associated regions with the carrying out of the Common Market. With the European Neighbourhood Policy (ENP) of 2004, the EU also provided for the contribution of regions to the stabilization of external borders and provided them with a financial tool, the European Neighbourhood Policy Instrument, in order to accomplish this task. The role of regions in Regional Policy was further reinforced in 2007, when the European Commission introduced the objective of territorial cooperation, with the aim of having regions contribute to European economic and social cohesion through their “small” foreign policy. Finally, since the creation of the European Grouping of Territorial Cooperation (EGTC) in 2007, local authorities can formalize external relations with their European neighbours and set up transnational legal structures. With the adoption of the Third Protocol of the Madrid Convention on Transfrontier Cooperation in 2009, the Council of Europe prepared for the implementation of a similar legal instrument, the Euroregional Cooperation Groupings (ECG), which is destined for the border regions of the Council of Europe's 47 member states. This legal instrument notably enables local and regional authorities of non-EU members to conduct neighbourhood policy and to thus contribute to the stabilization of the European continent.
In France, territorial diplomacy has recently evolved with the adoption on December 13, 2000, of a new legal framework recognizing the ability of overseas local and regional authorities to intervene in negotiations and, in certain circumstances, to sign agreements with sovereign nations. For instance, this law enabled French Guiana to directly formalize relations with Brazil. A new bill from July 22, 2015 would expand this possibility to all French local and regional authorities in an effort to facilitate territorial diplomacy. Nevertheless, these measures always provide for the external action of local and regional authorities to be authorized by the state and to be compatible with and complementary to the “main” foreign policy.