IT is trite law that good reasons must be given to justify infringements of fundamental rights protected by the European Convention on Human Rights, as incorporated into domestic law by the Human Rights Act 1998. But what reasons can one count as good reasons? In Re Brewster's Application [2017] UKSC 8; [2017] 1 W.L.R. 519, the United Kingdom Supreme Court addressed the question of how much deference courts should afford to post hoc rationalisations of decisions challenged for non-compliance with the Convention. The answer given by Lord Kerr, with whom Lady Hale, Lord Wilson, Lord Reed and Lord Dyson agreed, is interesting in its own terms and may have implications outside the confines of the Convention.