The House of Lords Constitution Committee today issues its main report on the European Union (Withdrawal) Bill. This follows the preliminary and interim reports on the Bill that the Committee published last year. The new report is wide-ranging and hard-hitting, the Committee’s view being that the Bill ‘risks fundamentally undermining legal certainty’. In this post, we make no attempt to summarise the report. Rather, we focus on two key and interlocking chapters that address the legal nature and constitutional status of the new body of domestic law – ‘retained EU law’ – that the Bill will create. In doing so, we highlight the Committee’s view that central parts of the Bill are ‘conceptually flawed’ and that relevant retained EU law should be reconceived by treating it as if it were contained in an Act of Parliament enacted on ‘exit day’.