In Spain, the political and administrative powers are shared between the State and the Autonomous Communities. Because of this, Autonomous Communities are required to participate in the functioning of the European Union together with the representatives of the Spanish State.

Furthermore, and according to the Spanish Constitution, the different Statutes of the Autonomous Communities and the corresponding legal provision, the implementation of European regulations (legislative development and administrative implementation,) depends on who has the competence. Therefore, Autonomous Communities act as guarantors of the correct execution of the European laws within their fields of competence and according to what is recognised by the relevant Statutes of Autonomy. Institutional relations between the Spanish local and regional authorities in the compliance and enforcement of European law is based on the following principles; institutional autonomy, no infringement of sphere of competence and loyal cooperation.

In Spain, since the '90s, new instruments for cooperation between the State and the Autonomous Communities have been implemented in order to detail the latter's participation in European affairs. The starting point was the Spanish Conference on Issues Related to European Communities (CARCE), now called the "Conference for European Union Affairs" (CARUE), which held its first meeting in 1989. This Conference consists of the competent Minister for public administrations, a Ministry of each Autonomous Community, a Government Council of Ceuta and Melilla, and the Secretaries of State for the EU and for the Territorial Administrations.

Within this Conference different formula for participation in the internal procedures, for the fulfilment of obligations, have been established with community institutions.

Finally, the regions have created organisations and networks to defend their interests before the European Union through the creation of a kind of regional lobby that follows the implementation of the policies of the European Union in order to ensure that the interests of the regions which are members of the networks are represented.