The entry into force of the Lisbon Treaty poses anew the question of whether, from now on, it will be more likely for the European Union to use this mechanism, or, conversely, the new institutional, jurisdictional and decision-making framework may act as a containment of favourable trends in the development of variable integration formulas. In reality, flexible or differentiated integration instruments, within or outside of the framework of the EU, alongside strictly intergovernmental cooperation between certain EU countries, have existed since the beginning of Community integration.
