Advocate General Campos Sánchez-Bordona has this morning given his opinion to CJEU in the Wightman case regarding whether UK can unilaterally withdraw notice of its intention to leave the UK under Article 50.
The AG's view is that it can. The reasons he gives are essentially threefold.
First, although not explicitly found in Article 50 itself, the ability to revoke a notification of withdrawal from an international treaty before it takes effect is found in Article 68 of the Vienna Convention on the Law of Treaties.
Second, the ability to pull out of the Article 50 process is compatible with the wording of Article 50 itself. The notification given under Article 50 is notification of an intention to leave, not a decision, and such an intention may change. In addition, withdrawal from an international treaty is a unilateral act of a member state and an expression of its sovereignty. That unilateral nature is mirrored in the initiation of the Article 50 process (through the initial notification) and should be projected forward to apply during the subsequent negotiation phase. A decision to leave must also be made in line with a state's constitutional procedures. Where a decision to remain was made in line with those same procedures it would rob the notification to leave of its constitutional legitimacy.
Finally, until the Article 50 process has run its course - either through the conclusion of a withdrawal agreement or by expiry of the two year timescale from notification (or any extended period) - the withdrawing state is still a member of the EU. In circumstances where the withdrawing state decided that it wanted to remain, it would be illogical for the EU to, in effect, expel that state such that it would have to apply for readmission.
Advocate General opinions are advisory only. However, CJEU does follow them around 80% of the time. Therefore, although a date for the full judgment has yet to be given, and may not be available before MPs vote on the withdrawal agreement on 11 December (if that date holds), this opinion may be taken as a strong indication of the way in which CJEU will go.
As we have previously commented, that is important as the ability to reverse out of Article 50 gives MPs an important additional option should they wish to vote down the current deal - or should they want to provide space for a general election or second referendum and for some reason the EU27 refuse to extend time under Article 50.