How in legal terms does the UK withdraw from the EU?

K&L Gates considers the legal implications for the UK leaving Europe

The process of a country joining the EU is well understood.  However, the referendum on the UK’s membership of the EU focuses minds on how EU membership can be reversed.

Article 50 of the EU Treaty basically permits any EU Member State to decide to withdraw from the EU “in accordance with its own constitutional requirements”. The procedure under Article 50 has never before been used and is thus untested.

The procedure would involve: (i) the UK giving notice to withdraw to the European Council; (ii) negotiation by the UK and the EU of a withdrawal agreement to govern the terms of the UK’s exit; (iii) if no withdrawal agreement is reached after two years (and the UK and all other Member States have not unanimously agreed to extend the deadline), the EU Treaties automatically cease to apply to the UK.   Any withdrawal agreement would also need to be ratified by most if not all national parliaments of the remaining Member States and also by the European Parliament.

From the UK perspective, the question remains open as to when a decision to withdraw from the EU is taken “in accordance with its own constitutional requirements” for the purposes of Article 50?

These are uncharted waters, but arguably the UK’s right to give notice under Article 50 should be regarded as a power for UK Government to exercise. Nevertheless, there is also the question of what process, beyond the Article 50 notification, is required to detach the UK from the EU?

This would depend partly on the form that any withdrawal agreement takes and/or if the UK exits by default after two years. If for example, there is a withdrawal agreement and that agreement is effected by way of a treaty, it would be normal to expect it to be dealt with under Crown prerogative powers to conduct foreign affairs, which could be exercised by the Government. However, it would be surprising if the terms of such an important agreement would not be debated and/or approved by Parliament (the same point could equally be made in respect of the Article 50 notification).

Regardless of prerogative powers, Part 2 of the Constitutional Reform and Governance Act 2010 gave statutory effect to the 21-sitting day ‘Ponsonby Rule’ of laying before Parliament treaties before actual ratification. If the Commons resolves against ratification, the treaty can still be ratified if the Government lays a statement explaining why the treaty should nonetheless be ratified and the House of Commons does not resolve against ratification a second time within 21 days (this process can be repeated ad infinitum).

Furthermore, the withdrawal agreement would potentially have to be implemented by new legislation. The European Communities Act 1972 might need to be repealed (or possibly amended), and other legislation implementing EU law would be similarly affected. It is not difficult to envisage a drawn-out process of creating and/or repealing relevant legislation, each piece of which would be subject presumably to normal Parliamentary approval/voting processes.

Moreover, at both the EU and UK levels we are in an unprecedented situation and, should the British people vote to leave the EU, new legal precedent will need to be created.