The UK Parliament remains sovereign over Scotland, Wales and Northern Ireland in that it could:
- legislate on devolved matters, a right expressly preserved by, for example, the Scotland Act 1998, and
- reverse or amend the process. The process is reversible because devolution is itself a product of UK statutes.
However, by a constitutional convention known as the Sewel Convention the UK does ‘not normally’ legislate on devolved matters without the consent of the relevant devolved body. But since this is a convention, rather than a rule of law, it does not have binding legal force and in 2018 the Scottish government’s refusal of consent for the European Union (Withdrawal) Bill did not prevent it from receiving Royal Assent. This convention remains legally unenforceable despite being codified in law by the Scotland Act 1998, s28(7) (see footnote above).
 Scotland Act 1998, s28:
1) Subject to section 29, the Parliament may make laws, to be known as Acts of the Scottish Parliament.
7) This section does not affect the power of the Parliament of the United Kingdom to make laws for Scotland.
8) But it is recognised that the parliament of the United Kingdom will not normally legislate with regard to devolved matters without the consent of the Scottish Parliament.
 As confirmed by the Supreme Court in Miller No. 1: R(Miller) v Secretary of State for Exiting the European Union  UKSC 5.