sentences:  The Lisbon Treaty made the first provision of a member state to leave.The procedure for a state to leave is outlined in which also makes clear that "Any Member State may decide to withdraw from the Union in accordance with its own constitutional requirements".Although it calls for a negotiated withdrawal between the seceding state and the rest of the EU, if no agreement is reached two years after the seceding state notifying of its intention to leave, it would cease to be subject to the treaties anyway (thus ensuring a right to unilateral withdrawal).