A Promise is a Promise: Article 50 TEU as grounds for the Application of the Principle of Promissory Estoppel in Withdrawal Cases

On 10 December 2018, the European Court of Justice (ECJ) ruled that the United Kingdom (UK) could, on the grounds of Article 50 TEU, unilaterally revoke the notification of its decision to withdraw, transmitted to the European Council on 29 March 2017. Given the political and economic implications of Brexit for the UK, and considering the constitutional nature of the EU legal order, the ECJ’s ’green light’ for the potential ‘changes of heart’ of the withdrawing Member State seem understandable. Another reading of Article 50 TEU is, however, possible. If this Article was interpreted in light of the principles of legal certainty and legitimate expectations, one could argue that, although unilateral, the notification of a Member State’s intention to leave the Union does have a certain binding force for both that State and for the Union institutions, in so far as the former commits to accomplish a future act and the latter rely on this commitment. Article 50 TEU can therefore be interpreted as providing grounds for a Member State to make a promise to withdraw and for the raising of a defensive shield aimed at preserving the effects of that promise via the application of the principle of promissory estoppel.