The question considered by the Supreme Court in Lipton, and the Interpretation Act (or accrued rights) analysis In Lipton v BA Cityflyer, the Supreme Court (UKSC) considered, obiter, how the European Union (Withdrawal) Act 2018 (EU(W)A 2018) applies in time—specifically, whether its provisions about retained EU law (REUL) must be applied by the court to disputes involving facts that occurred before IP completion day at the end of 2020, and to rights and liabilities already accrued by then. For the sake of simplicity, in this Q&A, cases involving facts that occurred before IP completion day are referred to as ‘pre-Brexit cases’, while those based on facts that occurred after IP completion day are referred to as ‘post-Brexit cases’. On one view, the answer to the question is that the provisions of EU(W)A 2018 relating to REUL and assimilated law do not apply in pre-Brexit cases. The temporal application