Relationship to EU law
On ‘exit day’, the EU (Withdrawal) Act 2018 will repeal the ECA. Under the terms of Part 4 of the Withdrawal Agreement, it will be necessary to ensure that the EU Treaties and other EU law continues to apply in the UK during the implementation period. This will be achieved by way of transitional provision, by which the Act amends the EU (Withdrawal) Act 2018 so that the effect of the ECA (modified as described below) is saved for the time-limited implementation period.
	The Act also modifies the saved ECA provisions to reflect the fact that the UK has left the EU, and that the UK’s relationship with EU law during this period is determined by the UK’s obligations under the Withdrawal Agreement, rather than as a Member State. The Act will also make sure that existing legislation continues to operate properly during the implementation period, despite the fact that the UK is no longer a Member State. As such, the Act will provide glosses to make clear how EU terms on the UK statute book should be read during the implementation period. For instance, the devolution statutes limit the devolved institutions’ competence by reference to EU law. The definition of EU law is, for these purposes, tied to the ECA: it means the rights, obligations etc arising under ‘the Treaties’ as defined in the ECA. The Act preserves the effect of the ECA for the purposes of the implementation period, and modifies the definition of ‘the Treaties’ and ‘the EU Treaties’ to include Part 4 of the Withdrawal Agreement. Therefore, during the implementation period, the references to ‘EU law’ in the devolution statutes will be read in light of Part 4 of the Withdrawal Agreement and those references will continue to impose restrictions on the competence of the devolved administrations and legislatures, as they did during the period of the UK’s membership of the EU.