▁have ▁been ▁rad ically ▁transformed . ▁ ▁Pro cedure ▁ ▁Article ▁ 5 0 ▁of ▁the ▁Tre aty ▁on ▁European ▁Union , ▁en act ed ▁by ▁the ▁Tre aty ▁of ▁Lis bon ▁on ▁ 1 ▁December ▁ 2 0 0 9 , ▁introduced ▁for ▁the ▁first ▁time ▁a ▁procedure ▁for ▁a ▁member ▁state ▁to ▁withdraw ▁volunt arily ▁from ▁the ▁EU . ▁The ▁article ▁states ▁that : ▁ ▁This ▁provision ▁does ▁not ▁cover ▁certain ▁over se as ▁territ ories ▁which ▁under ▁T FE U ▁Article ▁ 3 5 5 ▁do ▁not ▁require ▁a ▁full ▁treat y ▁revision . ▁ ▁Inv ocation ▁Thus , ▁once ▁a ▁member ▁state ▁has ▁not ified ▁the ▁European ▁Council ▁of ▁its ▁intention ▁to ▁leave , ▁a ▁period ▁begins ▁during ▁which ▁a ▁withdraw al ▁agreement ▁is ▁negoti ated , ▁setting ▁out ▁the ▁arrang ements ▁for ▁the ▁withdraw al ▁and ▁out lin ing ▁the ▁country ' s ▁future ▁relationship ▁with ▁the ▁Union . ▁Com men cing ▁the ▁process ▁is ▁up ▁to ▁the ▁member ▁state ▁that ▁int ends ▁to ▁leave . ▁ ▁The ▁article ▁allows ▁for ▁a ▁negoti ated ▁withdraw al , ▁due ▁to ▁the ▁complex ities ▁of ▁leaving ▁the ▁EU . ▁However , ▁it ▁does ▁include ▁in ▁it ▁a ▁strong ▁imp lication ▁of ▁a ▁un il ater al ▁right ▁to ▁withdraw . ▁This ▁is ▁through ▁the ▁fact ▁that ▁a ▁state ▁would ▁decide ▁to ▁withdraw ▁" in ▁accord ance ▁with ▁its ▁own ▁constitution al ▁requirements " ▁and ▁that ▁the ▁end ▁of ▁the ▁treat ies ' ▁application ▁in ▁a ▁member ▁state ▁that ▁int ends