Book excerpt: Sunset clauses are a commonly used statutory provision related to the temporary duration of various laws. This book explores the constitutional value of such clauses. It examines the drafting of sunset clauses and the relevant amendment process, as well as the parameters that influence their incorporation into legislation. Arguments and conclusions are drawn from historical and current uses and it is discussed how and why legislators draft legislation with sunset clauses. Predominantly focused on their use in the UK, the approach is interdisciplinary and comparative insofar as it uses examples from a variety of legal orders.