An in-depth analysis of the transition of European Union (EU) law within the United Kingdom's legal framework, charting the journey from membership through Brexit. The first source explains the structure of EU law, detailing its foundation in treaties (primary law) and secondary legislation (like regulations and directives), emphasizing the key principles of supremacy and direct effect which compelled member states to prioritize EU law. The second source outlines how the UK initially incorporated EU law via the European Communities Act 1972, and subsequently created retained EU law through the European Union (Withdrawal) Act 2018 post-Brexit, a body of law that lost its supranational status but temporarily maintained supremacy over pre-existing domestic law. Finally, the third source details the final stage of the transition through the Retained EU Law (Revocation and Reform) Act 2023, which effectively ends the supremacy of EU law, converts remaining retained laws into assimilated law by the end of 2023, and grants ministers extensive powers to amend or revoke this legislation.