Does Statute of Westminster 1931 prove the UK electorate and Parliament aren't sovereign in this instance?

Question

Doesn't Statute of Westminster 1931

1. violate Parliamentary Sovereignty (adduced below)?

2. and discredit Dicey's two assumptions that the UK electorate is the political sovereign, and its political sovereignty is ultimately supreme?

And whereas it is meet and proper to set out by way of preamble to this Act that, inasmuch as the Crown is the symbol of the free association of the members of the British Commonwealth of Nations, and as they are united by a common allegiance to the Crown, it would be in accord with the established constitutional position of all the members of the Commonwealth in relation to one another that any alteration in the law touching the Succession to the Throne or the Royal Style and Titles shall hereafter require the assent as well of the Parliaments of all the Dominions as of the Parliament of the United Kingdom:

[I skipped two paras.]

And whereas the Dominion of Canada, the Commonwealth of Australia, the Dominion of New Zealand, the Union of South Africa, the Irish Free State and Newfoundland have severally requested and consented to the submission of a measure to the Parliament of the United Kingdom for making such provision with regard to the matters aforesaid as is hereafter in this Act contained:

Clearly if Statute of Westminster 1931 "require the assent as well of the Parliaments of all the Dominions", then the UK electorate and Parliament can't alter Statute of Westminster 1931, thus neither aren't sovereign here.

Public Law: Text, Cases, and Materials (2019 4 edn). p 55.

A.V. Dicey, Introduction to the Study of the Law of the Constitution (1885; 10th edn 1959, London: Macmillan & Co.), pp. 39–40.

The principle of Parliamentary sovereignty means neither more nor less than this, namely, that Parliament [. . .] has, under the English constitution, the right to make or unmake any law whatever; and, further, that no person or body is recognised by the law of England as having a right to override or set aside the legislation of Parliament. A law may, for our present purpose, be defined as “any rule which will be enforced by the Courts”. The principle then of Parliamentary sovereignty may, looked at from its positive side, be thus described: Any Act of Parliament, or any part of an Act of Parliament, which makes a new law, or repeals or modifies an existing law, will be obeyed by the Courts. The same principle, looked at from its negative side, may be thus stated: There is no person or body of persons who can, under the English constitution, make rules which override or derogate from an Act of Parliament, or which (to express the same thing in other words) will be enforced by the Courts in contravention of an Act of Parliament.

Dicey’s definition was considered by a House of Commons select committee in 2010:

House of Commons European Scrutiny Committee, The EU Bill and Parliamentary Sovereignty, Tenth Report, Session 2010– 11, Vol. I (HC 633)

What is meant by Parliamentary sovereignty?

23. In the light of the evidence submitted to the inquiry we concluded, agreeing with Professor Bradley, that the term “Parliamentary sovereignty” bears a number of meanings which can get confused. We prefer to use the term the “legislative supremacy of Parliament” in this Report for the reasons so clearly set out by Professor Bradley: “Dicey’s Law of the Constitution made famous the phrase ‘the sovereignty of Parliament’, but a more exact term for the legal doctrine is ‘legislative supremacy’, whereby the power of the Queen- in- Parliament to legislate is subject to no legal limitations, and the courts have no power to review the validity of Acts of Parliament. This doctrine is always considered to be subject to the limitation that Parliament is unable to bind its successors (a matter to which I return briefly below). An advantage of using the term supremacy rather than sovereignty is that it enables the supremacy of EU law to be balanced against the supremacy of national law.”

Mark Elliott. Public Law (3 ed 2017). p 232.

6.2 What does ‘parliamentary sovereignty’ mean?

Orthodox constitutional doctrine says,280 and the courts generally appear to accept,281 that Parliament is sovereign. There is no legal limit to the laws that it may enact: any restraint that Parliament exercises therefore flows from the political, not the legal, system. Dicey observed that the flip side of this coin is that no one can lawfully override, derogate from, or set aside an Act of Parliament.282

Answer 1

The Statute of Westminster is an Act of Parliament so can be repealed by a subsequent parliament.

As such, it no more limits Parliamentary Sovereignty than any other Act.

Answer 2

The European Union Act 2011 prohibited Parliament and the government from accepting any new treaty extending or replacing the UK’s EU membership without first holding a referendum on that treaty. Since the government found it would be inconvenient to have to put the Brexit treaty to a referendum, they just quietly repealed it. Because it didn’t actually bind future Parliaments.

And the case you ask about is the same — it just means that if Parliament wanted to change the succession rules unilaterally it would have to pass two laws, the first to repeal the law saying it can’t do that, and the second to make the actual change.

Answer 3

This is a special case of the UK Parliament legislating for the independence of the Dominions (or recognising in law the already existing reality of their independence as set out at the Balfour Conference, if you prefer).

In constitutional theory this does not affect parliamentary sovereignty because it does not stop any UK Parliament in future passing an Act declaring that Canada is a colony again! And that would then be the position in UK law.

But of course making such a law would have no actual effect on the ground apart from provoking a major diplomatic incident.