Now that Theresa May, the UK Prime Minister, has received Parliamentary approval to trigger Article 50 of the Treaty on European Union (TEU), the UK is expected to formally notify the European Council of its intention to leave the European Union by the end of March.
The timelines for negotiations for the UK's exit from the EU and for establishing a new relationship between the European Union and the UK now start. Here is an overview of the next steps.
Phase 1: Separation
Article 50 envisages that the negotiations leading to the withdrawal of the United Kingdom from the European Union will last for two years, unless the European Council, in agreement with the UK, unanimously decides to extend this period.
In reality, the negotiation period is more likely to last less than eighteen months, given the formalities at European Council and European Commission level that first have to be gone through to formulate and agree the EU's negotiating position. There is also pressure for the process to be concluded before the next European Parliament election, which is scheduled for May/June 2019.
The first step is for the remaining 27 EU Member States to formulate guidelines for the European Commission to use in negotiations with the UK. On the basis of these guidelines, the European Commission will submit recommendations for the conduct of the negotiations to the Council.
The Council will then adopt a formal decision, authorising the opening of negotiations, and adopt negotiating directives specifying the substance of the negotiations and the detailed institutional arrangements required. Building in time for translation into all the EU's official languages, these formal preparatory requirements are expected to take at least three months following the trigger of Article 50. Therefore, the EU and the UK will not formally enter into negotiations before July/August 2017.
In addition, an agreement between the two sides will have to be reached by December 2018 at the very latest, as it is likely that the exit agreement will have to be ratified by the national parliaments on both sides in accordance with their constitutional procedures.
At latest, to comply with the two-year period specified in Article 50 TEU and to have the withdrawal agreement in force by the next European elections, the whole negotiating process will have to be completed by April 2019.
Given the multitude and complexity of the issues on the table and the fact that most of the time pressure will be on the UK, with the EU Member States taking a rather relaxed view, our current assessment is that it is unlikely that this two-year period will be extended by a (required) unanimous decision of the 27 remaining Member States in the European Council.
One question that needs to be settled in parallel with the separation negotiations relates to the revocability or otherwise of the Article 50 exit notice.
Although the UK Government is adamant that the legal effect of Article 50 is irrevocable once triggered, international treaty law has a role to play. Article 68 of the Vienna Convention on the Law of Treaties 1969 states that a party that gives notice of its intention to withdraw from a treaty can revoke that notice at any time before it takes effect.
But the legal position is not clear and there is a question mark over whether the Vienna Convention even applies: One view holds that the TEU creates an autonomous and special legal order which should not be interpreted by reference to other external international standards and that Article 50 amounts to a complete code for withdrawal. The TEU itself is silent on the position and the travaux préparatoires provide no conclusive guidance.
The question of whether the notice can be revoked or not could have considerable significance in terms of tactics around exit negotiations. In the view of the EU institutions and a majority of the remaining Member States, this is more of a political than a legal question. There is general consensus in Brussels that once the UK triggers Article 50, there is no turning back.
However, since the UK Government is adamant that the invocation of Article 50 TEU is irrevocable and hence constitutes in itself the de facto departure from the EU, this could also mean that the UK is - strictly interpreted - not bound by all the obligations of an EU Member State once Article 50 is triggered. This would include the contentious point of the UK's ability to negotiate bilateral trade agreements with third countries.
At present, the question of the revocability of Article 50 is in the early stages of consideration before the Irish courts.
In parallel with the separation negotiations, discussions on the future arrangement of the EU-UK relationship could begin during this phase. However, it is unlikely and impossible (because of procedural requirements on the EU-side) that both the separation deal and the future relationship could be defined and finalised within the two year window. Legislative procedures - not even the politics - already stand in the way of such an approach.
Act 2: Transition
Once the separation is final, with or without an agreement, the two sides are likely to enter a period of transition. Both sides will need to assess where they stand after the two-year negotiation period. Since the TEU does not specify anything beyond the initial two-year negotiation period, in a legal sense the 27 remaining EU Member States and the UK will enter uncharted territory once the separation phase is over and while negotiations around the new relationship have yet to begin.
There is no time limit on the transition period. But it is likely to take at least six months to allow the dust of the separation to settle and to fully identify the areas where a new EU-UK relationship looks most promising and those areas that will need more attention.
The UK Government also plans to introduce a Great Repeal Bill, which will remove the European Communities Act 1972 (which currently gives direct effect to all EU law in the UK) and will convert the body of existing EU law into UK law. In practice, it is likely that the UK Government will not convert all existing EU law into national law, but instead will pick and choose what should remain. In addition, EU legislation that remains will have to be amended to reflect the fact that the UK is no longer an EU Member State.
In parallel, the EU will have to "de-Anglify" all its existing regulations and treaties with third parties, i.e. remove all references to the UK as a Member State of the European Union. This in itself may have far-reaching consequences, especially as regards the EU's relationship with third countries.
The removal of the UK from a (free trade) treaty will substantially alter the third country's perception of the nature of and the rationale for the original agreement. Some of the EU's partners will probably demand renegotiation of existing agreements, on the basis that the UK's departure constitutes a fundamental alteration to the agreement and a shrinking of e.g. the market potential for certain goods and services.
Furthermore, in the absence of a separation agreement and in anticipation of a specific EU-UK free trade agreement, trade relations between the EU and the UK will be governed by general WTO-rules, including the WTO-specifications for tariffs.
Although the UK Prime Minister appears confident about the willingness of third countries to conclude bilateral trade agreements with the UK, it is important to underline that for the UK these negotiations are likely to be long and complex.
In addition, if the UK is going to maintain a constructive environment for the conclusion of its most important trade agreement - i.e. with the EU - the UK is unlikely to be in a position to substantially deviate in these new agreements from trade standards previously agreed within the EU context.
Therefore, in the absence of a conclusive and comprehensive agreement with the EU, the UK cannot be expected to make significant concessions to third countries on standards governing trade, as this will negatively affect its negotiations with the EU.
In addition, the UK will have to deal with domestic political issues. The Scottish First Minister, Nicola Sturgeon, has recently announced a plan to hold a new referendum on Scottish independence. This will distract from the Brexit agenda.
Act 3: Reengagement
The UK's negotiations with the EU on its new relationship with the EU and a potential trade agreement will be conducted in accordance with the rules that govern the EU's relationship with third countries, because by this stage the UK will be a third country like any other non-EU Member State.
Both parties will have to assess what agreement is in its best interests. While the UK Government has announced its desire to conclude a new strategic partnership with the EU, including a comprehensive Free Trade Agreement and a new customs agreement, the EU has still not expressed its views on this matter. "First things first" has been the motto for the EU - the focus is on the exit process and the possibility of an exit payment, rather than on the future relationship.
Whatever the format of such an agreement, it is likely to require an extensive negotiation process and may take years to be finalised. After an agreement has been reached, it will likely have to be submitted for ratification to the national procedures of the 27 EU Member States. Much like the Canada-Europe Trade Agreement (CETA) in 2016, the new EU-UK agreement will have to pass all layers of (sub)national parliamentary scrutiny in the EU, before finally entering into force.
If Scotland were to vote for independence in due course, the EU would find itself negotiating a new relationship with two additional sovereign entities in its immediate neighbourhood. Another contentious issue will be the possible cost of Brexit for the UK, the so-called Brexit Bill. This will be the subject of another DLA Piper alert.
To conclude, the EU and the UK have entered uncharted territory where many legal issues remain unsolved on principle. The UK's exit from the EU promises to be tough and the outcome of the negotiations remains far from uncertain.