The withdrawal of the United Kingdom from the European Union after 44 years poses unprecedented legal challenges. EU secondary legislation and EU related legislation is evident across the whole spectrum of the UK statute books and regulates the conduct of businesses and citizens alike. After Brexit the paramount question is what is going to happen with all these laws. The UK government intends to adopt the Great repeal bill, an elephantine law, to repeal on the one hand the European Communities Act and on the other hand to transpose the EU secondary legislation - regulations and directives already enforceable in the UK - into domestic laws.
Without doubt, this is a herculean task, necessary to safeguard legal certainty and maintain a stable legal environment. In principle, the UK Parliament will have to examine every bit of EU secondary legislation and convert it into domestic law by amending some provisions and repealing others. But this would be time consuming and will clog the parliamentary business. On the other hand, the executive, due to its expertise, is placed in a better position to accomplish this role in a more efficient way. Therefore, Parliament can delegate this task to the UK government.
This is actually the proposed solution as it is stated in a recent white paper published by the Government. But such wide delegated powers must be subject to safeguards against constitutional risks. The Select Committee on the Constitution has accurately remarked that ‘one tool available to Parliament to reduce the constitutional risks associated with wide-ranging delegated powers is sunset clauses.’
Indeed, sunset clauses - statutory provisions providing for instance that the delegated power will expire automatically on a particular date - are the appropriate apparatus to allow wide delegated powers and simultaneously enhance the parliamentary oversight during the whole process. Unless re-authorised by the legislature, a sunset clause brings about the expiration of the delegated power on a prescribed date. In practice, the benefits from the sunset clause in the Great Repeal Bill are twofold. First, such clause sets the timetable for the whole process of the transposition the EU secondary legislation into domestic laws advancing legal certainty. Second, such clause as an alarm clock creates the incentive for the comprehensive legislative evaluation of the delegated powers minimizing the risks from the abuse of such powers.
Brexit is a moment of historical gravity for the UK and it does not surprise us the fact that legislators discuss the use of sunset clauses in the Great Repeal Bill. Likewise, during past historical lawmakers have relied on and employed sunset clauses. Suffice to mention here two events. First, just before the outbreak of the Civil War, in 1625, sunset clauses were used by the Commons in order to assert authority over taxation and to circumscribe the power of the Crown. Second, in 1704 when the Parliament of Scotland passed an act, which provided that the Kingdom of Scotland has the power to choose a monarch who might not be the same person as the monarch of the English throne, the Parliament of England responded with an act subject to a sunset clause imposing economic restrictions on Scottish in order to promote the unification between the Kingdom of England with the Kingdom of Scotland.
The delegation of the legislative powers, subject to a sunset clause, is a common practice for the western democracies: suffice it to mention the example of Italy, Spain, France and Greece. In the UK, the Donoughmore Report has emphatically stressed that sunset clauses are a desirable mechanism to prevent abuse of delegated power. A fortiori, the use of sunset clauses in such a broad delegation of powers as that suggested in the Great Repeal Bill is a constitutional imperative that stems from both the separation of powers and parliamentary sovereignty.
Dr Antonios Kouroutakis is Assistant Professor at IE University.
 In fact ‘13.2% of UK primary and secondary legislation enacted between 1993 and 2004 was EU related’ see Jack Simson Caird, Legislating for Brexit: the Great Repeal Bill, Briefing Paper No 7793 (House of Commons Library) 5.
 About the Great Repeal Bill see Jack Simson Caird, Legislating for Brexit: the Great Repeal Bill, Briefing Paper No 7793 (House of Commons Library) 5.
 Antonios Kouroutakis, The Constitutional Value of Sunset Clauses (Routledge 2017) 49.
 Antonios Kouroutakis, The Constitutional Value of Sunset Clauses (Routledge 2017) 128.
 Constitution of Italy, Article 76.
 Constitution of Spain, Article 82 (3).
 Constitution of the Fifth Republic, Article 38 (1).
 Constitution of Greece, Article 43 (4).
 Committee on Ministers’ Powers, Report (Cmd 4060 1932).