This was intended to give effect to the UK's obligations as a Member State under the relevant EU treaties to comply with EU law.

Under section 2(1) of the ECA 1972, certain types of EU rights and obligations, which are intended to be directly effective, were given effect in the UK without the need for any further domestic legislation. This included rights in the EU treaties as well as EU regulations which contain detailed legal rules.

Other types of EU law were given effect through UK regulations made under section 2(2), or in some cases through separate Acts of Parliament. This included EU directives which set out broad outcomes or frameworks but which leave it to each Member State to make its own provision to achieve the required legal effect.

In terms of its application, EU law is 'supreme'. This means that where there was a conflict between EU law and UK domestic legislation, the latter could be disapplied - a principle which provided the only circumstance in which a UK court can disapply an Act of Parliament.

UK judges were also bound to follow decisions by the Court of Justice of the EU (CJEU) under section 3(1) of the 1972 Act.

Over the last 40 or so years, EU law has come to form a large part of the law which applies in the UK, covering a range of different issues. The UK has therefore not needed to – and indeed could not – formulate its own domestic laws in relation to such issues where EU law applied directly. Nor could it take a different approach to areas covered by EU Directives which required a particular approach to be taken in domestic legislation.

As of the point of its exit from the EU, the UK is no longer be subject to the EU treaties as it will no longer be an EU Member State. Directly applicable EU law will no longer apply to the UK under the EU treaties, nor will it be required by those treaties to ensure that domestic legislation meets the requirements set out in EU Directives.

Instead, the UK's relationship with the EU is now governed by the Withdrawal Agreement, a new international treaty negotiated by the UK and the EU under Article 50 of the Treaty on European Union. The Withdrawal Agreement is intended to –

  • tie up the administrative and financial loose ends from the UK's membership of the EU,
  • protect UK and EU citizens living in each other's territory, and
  • provide a stand-still period in relation to the application of EU law in order to allow for the negotiation of a trade deal, referred to in the Withdrawal Agreement as the 'transition period' and in UK legislation as the 'implementation period'. 1

On 26 June 2018, the European Union (Withdrawal) Act 2018 (EU(W)A 2018) received royal assent. Its purpose is to avoid the legal vacuum that would be created once EU law ceases to be applicable in the UK, given that much of our law has come from the EU through the EU treaties. As enacted, the EU(W)A made no provision for an implementation period despite the fact that the UK had signalled that it would seek one in Prime Minister May's speech in Florence on 22 September 2017.

The European Union (Withdrawal Agreement) Act 2020 (EU(WA) A 2020) was passed on 23 January 2020. It fulfils two functions. The first is to amend the EU(W)A 2018 to accommodate the implementation period set out in the Withdrawal Agreement, under which the UK will continue to be bound by EU law until at least 31 December 2020. The second is to make provision in UK law for other aspects of the Withdrawal Agreement, including citizen's rights, the financial settlement and the Ireland/Northern Ireland Protocol. The EU(WA)A 2020 thus contains a mix of amendments to the EU(W)A 2018, together with a number of substantive provisions.

This paper gives an overview of both the EU(W)A 2018 and the EU(WA)A 2020, as well as highlighting some of their interesting implications from a public law perspective. Given the connection between the two pieces of legislation, rather than discuss each in turn, a thematic approach is taken with discussion first centring on the application of EU law in the UK after Brexit – both during and after the implementation period – before moving on to how other aspects of the Withdrawal Agreement are given effect in domestic law.


The Withdrawal Agreement makes provision for an implementation period from the date of the UK's exit from the EU until 31 December 2020. This period is capable of a single extension of either one or two years by mutual agreement between the UK and EU.2

The intention is to provide a standstill period after the UK has officially left the EU during which businesses can adapt to the change, and the UK and EU can negotiate a future trade deal. As such, apart from participation in EU institutions and governance structures and some other exceptions, the UK will be treated as if it continued to be an EU Member State in EU law for the duration of the implementation period. 3 The legal foundation for this will be the Withdrawal Agreement rather than the EU treaties.

The UK will remain part of the EU single market and customs union and must continue to respect the four freedoms of movement of goods, people, services and capital, as well as continuing to apply the EU customs code to imports into the UK from third countries.

To facilitate this, under the Withdrawal Agreement, the UK will continue to apply most EU law during the implementation period as if it was still an EU Member State. Any changes or additions to EU law made during the implementation period will also apply. 4

However, under the EU(W)A 2018, the ECA 1972 – through which EU law currently applies in the UK – is due to be repealed on exit day. 5 'Exit day' is defined as 31 January 2020. 6 This would mean that directly effective EU law – such as EU regulations – would cease to have effect in the UK and the subordinate legislation made under the ECA 1972 to enact other forms of EU law would also fall away.

Rather than change the definition of exit day, the EU(WA)A 2020 inserted provisions into the EU(W)A 2018 which seek to preserve the effect of certain provisions of the ECA 1972 for the duration of the implementation period, with some amendments as to how those provisions are read. 7 This is to reflect the fact that the UK's relationship with the EU will be governed by the Withdrawal Agreement rather than by virtue of it being an EU Member State.

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1 This Practice Note will refer to the 'implementation period' as this is the term used in the UK legislation discussed.

2 Articles 126 and 132 Withdrawal Agreement.

3 Articles 7 and 127 Withdrawal Agreement.

4 Articles 4 and 127(1) Withdrawal Agreement.

5 Section 1 EU(W)A 2018.

6 Section 20(1) EU(W)A 2018.

7 Section 1A EU(W)A 2018.

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