This paper provides an overview of the Catalan law at the European context. How the Catalan institutions can tackle on the Spanish Government policies and decisions in front of the European Union. And how the European Union Law and policies are implemented in a decentralized country such Spain where Autonomous Communities have their own Governments and Parliaments. There will also be examined how this Spanish territorial decentralized structure affect the implementation of such EU norms and its control. Finally, there will be exposed how Catalan institutions manage to participate in front of the European Union institutions. Which are the instruments that can guarantee this participation and which are the EU responses to them.