Release Date 23 January 2017

The Supreme Court will determine tomorrow (Tuesday 24th January) whether the Government have power to give notice pursuant to Article 50 of the Treaty on EU of the UK's intention to withdraw from the EU without an Act of Parliament providing prior authorisation to do so. The PM has announced that she intended to ‘trigger’ Article 50 before the end of March 2017.

If an Act of Parliament is required, it must pass three readings in both houses; notably, the government does not have a majority in the Lords. It is highly likely that MPs and Peers will introduce amendments to the proposed legislation intended either to subject the negotiations to certain conditions (e.g. remain in the internal, or ‘single’ market), to require Parliamentary scrutiny throughout the negotiation process (e.g. statements at regular intervals), and/or to require that Parliament approve both the withdrawal agreement and the agreement on the future relations between the UK and the EU-27. The Liberal Democrats will propose an amendment requiring a referendum on the terms (as per their Autumn Party Conference motion).

The effect of Article 50(3) of the Treaty on EU is that, once notification is given, the UK will cease to be a member of the EU on either on the date of entry into force of a withdrawal agreement, or two years after the notice is given, unless that period is extended by agreement between the UK and the EU-27. For the Parliamentary role at the end of the negotiation process to be meaningful, the fundamental legal question is whether the UK could unilaterally withdraw its Article 50 notification, should Parliament (or the electorate, in a referendum) consider the agreement on the UK’s future relations with the EU-27 to be unsatisfactory.  It is important for both the UK and the EU Institutions to know the correct legal position. Politically, it is unlikely, but not impossible, that (some of) the EU-27 would not accept the UK’s request to revoke withdrawal and thus to remain in the Union.

In the proceedings in the High Court, the applicants (for legal reasons concerning the strength of their other claims) and the government (quite possibly for political reasons) asked the Court to proceed on an irrevocability assumption it is not clear whether the Supreme Court will make a substantive determination. However, it has been suggested that Article 50’s silence regarding withdrawal of notification means that general rules of international treaty law apply- particularly Article 68 of the Vienna Convention of the Law of Treaties, which states that a notice to withdraw ‘pursuant to the provisions of a treaty’ may be revoked at any time (assuming withdrawal has not yet occurred). On Friday 27th January, the Irish High court will hear a case (brought by Joylon Maugham QC) where the applicants are requesting a reference to the European Court of Justice (ECJ) on this matter.On 28 November 2016, 'British Influence' initiated proceedings based on the assumption that leaving the EU does not mean leaving the European Economic Area (EEA): the latter, they argue, requires separate notification under Article 127 of the EEA Agreement ('Each Contracting Party may withdraw from this Agreement provided it gives at least twelve months’ notice in writing to the other Contracting Parties.') Depending on the ratio of the forthcoming Supreme Court judgment on Article 50, this litigation (if successful) could potentially lead to the government being forced to bring forward separate legislation before notifying its intention to withdraw from the EEA agreement.