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Article 50 TEU
The Treaty base for EU withdrawal is Article 50 of the Treaty on European Union (TEU). This is usually considered the only legal way to leave the EU, although some have suggested there are other ways.
Notifying intention to withdraw
After a decision to leave the EU, the first step is for the UK to notify the European Council of the UK’s intention to withdraw.
There is no set timeframe for when it has to do so, or in what form.
It is likely that the notification would be done by the Prime Minister under prerogative powers. But arguments that Parliament should – or even would have to – give its consent have gained currency since the referendum.
There is no provision for withdrawing the notification, but some analysts believe the UK could change its mind about leaving the EU after notification and before actually withdrawing.
Notification would trigger the opening of withdrawal negotiations between the UK and the EU. The European Council would draw up a negotiating mandate (‘guidelines’) without the UK’s participation.
The EU negotiator would then negotiate a withdrawal agreement with the UK. The withdrawal agreement would be concluded by the EU Council by qualified majority (excluding the withdrawing state) after obtaining the consent of the European Parliament.
During the negotiations the UK would continue to participate in EU activities, the EU institutions and decision-making. But it would not take part or vote in any Council or European Council discussion concerning its withdrawal.
The negotiation period is two years from formal notification, but it could be extended if all Member States agreed.
The UK could still hold the EU Presidency in 2017 in spite of the vote to leave, although politically this could be very awkward.
The withdrawal agreement
The withdrawal agreement would contain whatever the negotiators wanted it to, but would probably set out the detailed withdrawal arrangements and transition provisions, taking into account the framework for the withdrawing State’s future relationship with the EU.
There are particular concerns about the continuation of the UK’s trading relations with third states and there is a question about possible vested rights for individuals and companies.
Agreement on future relationship with EU
It is not clear whether the UK’s future relationship with the EU would be covered by the withdrawal agreement or negotiated as a separate agreement alongside the withdrawal agreement. If it was a separate agreement, it could for example be an Association Agreement entered into by the leaving State, the EU and the remaining Member States, agreed by unanimity in the Council and with EP consent.
The UK could ask to join the European Free Trade Association (EFTA) and the European Economic Area (EEA). Membership of these organisations would not be automatic but subject to the unanimous approval of existing Members.
Voting on any separate post-exit agreement could require the unanimous agreement of EU Member States and EP consent.
If the UK wanted to re-join the EU in the future, it would have to re-apply under Article 49 TEU.
Release of EU obligations on withdrawal
Withdrawal would take effect either when a withdrawal agreement entered into force, or two years after notifying the European Council of the intention to withdraw (unless there is a unanimous agreement to extend the negotiations). If there is no withdrawal agreement after two years and a veto on an extension period, or if the leaving State does not like the agreement, it can leave the EU without a withdrawal agreement.
The other EU Member States could reject a withdrawal agreement, but they could not stop the UK from leaving the EU.
EU law ceases to apply to the withdrawing state upon withdrawal, but there might be some acquired rights for EU and UK citizens.
Dealing with EU law the UK has implemented
Having triggered the Article 50 process, the UK Government and Parliament would decide which EU-based laws, rules and regulations they wanted to keep, amend or repeal. The starting point is likely to be repealing the European Communities Act 1972, perhaps with savings provisions.
UK primary or secondary law implementing EU law and directly effective EU law could continue if the Government wanted and/or to the extent practicable.
The devolved legislatures would have to deal with EU legislation they have transposed into Scottish, Welsh or Northern Irish law. It would also be necessary to amend the relevant parts of the devolution legislation, which might require a Legislative Consent Motion under the Sewel Convention.