In “the constitutional case of the century”, the UK Supreme Court concluded that the Government did not possess the prerogative power to withdraw from the European Union. However, whilst it may be clear that legislation was required to empower the Government to notify the European Union of its intention to leave, it is not necessarily clear when legislation would be required to withdraw from international Treaties. There is also considerable controversy as to whether the Supreme Court reached the right conclusion. It is hard to determine how far Miller would apply to other international Treaties. At its broadest, it would apply to the withdrawal from any Treaty which had created rights for individuals, regardless of whether this Treaty had been implemented into domestic law or not. At its narrowest, it only applies to the European Union Treaties, which created a set of arrangements in international law that are so esoteric, they are unique to the European Union. To demonstrated how one judgment can generate such a plethora of interpretations, we need to revisit the original criticisms and unravel the different strands of argument running through the decision.