Remaining implementation of the Withdrawal Agreement
30 Article 4 requires that the provisions of the Withdrawal Agreement and the provisions of Union law made applicable by the Withdrawal Agreement produce "the same legal effects" in the UK as those which they produce within the EU and its Member States. In broad terms (and subject to the provisions of Article 4 itself), the intention is that the Withdrawal Agreement and the provisions of EU law applied by the Withdrawal Agreement have the same legal effects in UK domestic law as attached to EU law while were a Member State. One effect of this is that legal or natural persons will be able to rely directly on some of the provisions of the Withdrawal Agreement before the UK courts.
31 The approach in the Bill is intended to give effect to Withdrawal Agreement law in a similar way to the manner in which EU Treaties and secondary legislation were given effect through section 2 of the ECA. Although the ECA gives effect to EU Treaties and secondary legislation, it is not the originating source of that law but merely the ‘conduit pipe’ by which it is introduced into UK domestic law. Further, section 2 of the ECA can only apply to those rights and remedies etc that are capable of being ‘given legal effect or used’ or ‘enjoyed’.1
32 The approach in the Bill to give effect to Article 4 is to mimic this ‘conduit pipe’ so that the provisions of the Withdrawal Agreement will flow into domestic law through this Bill, in accordance with the UK’s obligations under Article 4. The approach also provides for the disapplication of inconsistent or incompatible domestic legislation where it conflicts with the Withdrawal Agreement. This ensures that all rights and remedies etc arising under the Withdrawal Agreement are available in domestic law.2 The approach in the Bill is explained in more detail in the commentary below.
33 In some circumstances, provisions contained in the Withdrawal Agreement require further detail to be set out in domestic legislation to ensure rights and obligations etc are given full effect in the UK legal system. For example, Article 159 of the Withdrawal Agreement creates an obligation to establish an independent authority to monitor the implementation and application of the citizens' rights part of the Agreement in the UK. Domestic legislation will be required to establish the authority and to define its powers and purpose in line with the Withdrawal Agreement.
34 In a further example, although a qualifying EU citizen can rely directly in UK courts on some of the provisions of the citizens’ rights part of the Withdrawal Agreement, further provision is required to ensure UK legislation gives full effect to and is compatible with those rights. The Bill makes provision for how these parts of the Withdrawal Agreement will be implemented.
1 R (on the application of Miller and another) (Respondents) v Secretary of State for Exiting the European Union (Appellant)  UKSC 5, paragraph 65. For further explanation of how EU Law applies in the UK please see http://www.legislation.gov.uk/ukpga/2018/16/notes/division/10/index.htm
2 This ‘conduit pipe’ does not apply to Part 4 of the Withdrawal Agreement which sets out the agreement on the Implementation Period.