A first question has been whether the UK government could trigger Article 50 TEU on its own and start the process of withdrawal without the involvement of the UK Parliament. In January 2017, the UK Supreme Court resolved this question in the Miller case, ruling that the June 2016 referendum did not automatically empower the UK government to start the withdrawal process without authorization from the UK Parliament. As a result, the UK government submitted a withdrawal bill to Parliament. The bill easily passed in the House of Commons, and despite the House of Lords’ willingness to propose amendments, it was eventually approved in its initial version by the House of Commons on 13 March 2017. This will allow the UK government to invoke Article 50 TEU and commence the withdrawal process before the end of March 2017.
A second question regards how the withdrawal negotiations unfold. According to Article 50 TEU, these should both handle the untangling of a departing member state from the EU legal order and define the new relationship between that country and the EU post-withdrawal. Article 50 TEU sets a two-year timeframe to agree on the terms of both the divorce and the new relationship, after which the exiting member state is simply out of the EU – the so-called cliff-edge. The European Council can extend the deadline, but this requires unanimous consent by the remaining 27 member states. Negotiations on liabilities are going to be contentious, and the EU has never concluded a comprehensive trade pact in just two years. So it is highly uncertain if the UK and the EU can manage to agree on a complete withdrawal deal and define the new relationship after the divorce within the given timeframe.
A third question arises, finally. Even if the UK and the EU are able to conclude a withdrawal agreement which covers both past and future relations, several uncertainties surround the process of ratification of this accord. On the basis of the EU Treaties, the European Parliament must ratify the agreement and the UK government has committed to submit the deal to an “up-or-down” vote before the UK Parliament. If either of these parliaments vetoes the agreement, the UK government and the EU institutions may be forced back to the drawing board, or leave with no deal.