UK law:

The UK can “cancel” its membership of the European Union by giving two years’ written notice to the European Council at anytime.

Unfortunately, UK law doesn’t tell us who’s entitled to give this notice, or when.

The prime minister has said that, if the UK votes to leave the European Union, he will give this notice immediately. However: the referendum result won’t be legally binding, and the prime minister’s likely to be under pressure to resign if the UK votes for #Brexit. So his ability to give this notice might be called into question for political and other reasons.

There is at least an argument that the prime minister cannot lawfully give the UK’s notice to quit, unless and until Parliament has debated and endorsed the UK’s referendum result – and that argument might be right.  However, it’s not yet clear whether anyone will try to run it. At least at first blush, there’s no point – Parliament is unlikely to choose “remain”, in the face of a referendum #Brexit result. But, if the result is close, and there are other reasons for running this argument, the chances of it being run and succeeding will increase. These “other reasons” might include: (a) that if the UK delays giving notice, it will give the Union time to consider and respond to the UK’s referendum result, and that might help the UK (and the European Union) avoid #Brexit, or some of the consequences of #Brexit; and (b) that two years will not give the UK and European Union enough time to negotiate sensible withdrawal terms. This period can only be extended in two ways – with the agreement of all 28 European Union Member States, or by delaying the giving of notice. Agreement may be hard to come by … so delay is the better course.

If the prime minister is under pressure to resign, or actually resigns, there might also be calls for an early UK general election.  Although an early general election is possible – for the moment, it’s unlikely. This is because, since the Fixed Term Parliaments Act 2011 came into force, the UK’s Parliamentary terms have been fixed at 5 years a piece. The next UK parliamentary general election will therefore take place on or (in exceptional circumstances) after Thursday 7 May 2020, unless the House of Commons passes:

• a motion “that there shall be an early parliamentary general election” and, if the motion is passed on a division, the number of MPs voting in favor is equal to at least two thirds of the number of seats in the house, including vacant seats; or
• a “no confidence in her Majesty’s Government” motion is passed by a simple majority of those voting, and that result is not undone by the passing of a “confidence in Her Majesty’s Government motion“, within a fortnight.

European law:

If the UK decides to leave the European Union, it will have to give notice to the European Council before formal UK / European Union withdrawal negotiations can begin. When that notice is given, the European Commission will make recommendations to the European Council about the conduct of the withdrawal negotiations; and the Council will take them into account before nominating a European negotiator, agreeing a set of negotiation guidelines, and authorizing the start of negotiations.

During the negotiation period, European law will continue to apply in and to the UK, and its citizens. As a result, for example, the UK’s MEPs will still be entitled to attend and vote in the European Parliament, and the UK will still be entitled to participate in Council and Committee meetings. However, the politics will almost certainly shift. If they do, the UK’s views will carry less weight after a #Brexit referendum result than they carried before. Practical difficulties may also arise in the community if there’s a widespread misunderstanding about the UK’s legal position, and the things it’s still lawfully entitled or lawfully prohibited from doing.

If the two year negotiation period expires without an agreement, either to extend the negotiation period, or on the UK’s withdrawal terms,  the UK’s membership of the European Union will lapse automatically. At that point, the UK will no longer be entitled to exercise the rights conferred on it under the European Treaties; but it won’t be bound to comply with European law either.

If the UK delays giving notice of its intention to leave the European Union, the Union and its institutions are likely to wait a reasonable period for that notice to be given. But that is all. If the UK seems to be dragging its heels in the hope of securing a political advantage at a European Union level, the European Union might take the announcement of the UK’s referendum result as the notice required to trigger the start of the two year negotiation / notice period. And, if the UK breaches European law by (for example) restricting the free movement of people from the European Union into the UK, the European Union might suspend the UK’s rights under the European Treaties, and invite the Commission to take infraction proceedings against the UK.

Interesting times may therefore be ahead.

[View source.]