I thought once the EU Constitution stated that once a member state triggered Article 11 and announced their intent to leave (which the UK has already done), they could not “retract” that and would have to apply for membership from scratch. If you think that the EU is infringing on the soverigenty of the UK now, just see what type of “re-entry” deal they get offered if Tony Blair comes hat-in-hand begging to be let back in...
If a State which has withdrawn from the Union asks to rejoin, its request shall be subject to the procedure referred to in Article 49.Article 49 is a short two-paragraph article that has to do with new members joining the EU.