discusses the relevance of the Statute of Westminster and whether parliamentary assent of the Realms is required. It also analyses the impact of such a change on a number of Realms, including Australia, New Zealand and Canada. It considers whether the British changes would automatically affect who becomes Sovereign in these Realms, or whether each Realm would have to change its own laws. In those Realms that are federations, consideration is also given to the source of constitutional power to make such legislative changes.Twomey asks -
In making changes to the law of succession to the throne, to what extent must the British Government consult with or seek the consent of other Commonwealth countries, especially the Commonwealth "Realms‟ of which Her Majesty is Head of State? Would a British legislative change to the rules of succession to the British throne have any impact upon who will be the Head of State in any other Commonwealth Realm? What difficulties might Commonwealth Realms face in changing their own laws and Constitutions regarding their Head of State?She concludes that -
While changing the rules of succession to the British throne might seem to be a relatively simple legislative exercise of updating ancient laws to make them more consistent with current anti-discrimination laws, it presents greater difficulties in other Commonwealth Realms. It is doubtful whether the commitment in the Statute of Westminster to obtain the parliamentary approval of the Dominions continues to be applicable, but as a matter of comity, consultation will still be necessary as changes to the law in the United Kingdom may have constitutional ramifications for Commonwealth Realms.
Sir Zelman Cowan once observed that the personal union of Crowns in the Commonwealth is distinctive in that "there are separate countries with a common law of succession and this fact binds these countries in constitutional links by virtue of the shared monarchy‟. If it is regarded as important to the United Kingdom that the Crown, while divisible in its sources of advice and exercise of powers, remain indivisible in its monarch (i.e. that it be held by the one person), then special care will need to be taken to ensure that all Commonwealth Realms are willing and able to make the necessary changes to succession in relation to their own jurisdictions. In some cases, there may be manner and form constraints upon constitutional change. In federations, there is the added complication of obtaining the consent of all the constituent polities. Even in unitary countries such as New Zealand, issues may arise with respect to self- governing dependencies. Finally, there is uncertainty in some Realms as to whether United Kingdom changes would affect the identity of the Sovereign within that Realm, even though the United Kingdom can no longer legislate for the Realm, or whether local legislative change would be needed. As most Commonwealth Constitutions were not drafted with such issues in mind, many do not deal with succession to the Crown at all.
Ultimately, however, the law of succession to the Crown of the United Kingdom is a constitutional matter for the United Kingdom to determine. No Commonwealth Realm has a right of veto upon such a change and consultation, although appropriate, does not pose a constitutional barrier to reform.