1.The regions in the European Union
     1.1. Concept of region
     1.2. Decentralized States

2. External participation: regional representation in the European Union
     2.1. Participation in institutions
     2.2. Participation in the organs

 3. Internal participation: Ascending phase. Participation in the national position on EU affairs
            3.1. The Spanish case
            3.2. The German case

4. The internal participation: Descending phase.  The implementation of Union law by the regions
           4.1. The Spanish case
           4.2. The German case

5. Constitutional mechanisms for the enforcement of EU law by the regions