Just details of EU history:
According to a Council document from June 2008 in which you find a summary of the preparatory work for the implementation of the Lisbon Treaty at that time (document version with handwritten comments), "many delegations" of EU member states thought that the SCIFA, the Council's Strategic Committee on Immigration, Frontiers and Asylum, should be abolished in order to streamline the Justice and Home Affairs (JHA) structures (see page 7).
However, in November 2009, right before the entry into force of the Lisbon Treaty, the Council decided to keep SCIFA until 2012.
This means that "many delegations" had changed their mind within one year regarding the streamlining of JHA structures.
Is Article 50 TEU Valid?
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