I wonder about that as well.
Does the Queen's Privy Council declaration simply mean that "female descendants who marry and their descendants" do not
automatically bear the surname Mountbatten-Windsor (in accordance with the British tradition that women and their children take their husband's surname)?
Or does it go beyond that and also prohibit female descendants from
adopting the surname for themselves and their children?
Likewise, although descendants in the male line
automatically bear the surname Mountbatten-Windsor, do they have the right to adopt another if they wish?
According to the government's website: "Under English law, a person may change their surname at will."
https://assets.publishing.service.g...e/594307/Name_change_-_English_April_2016.pdf
The Royal Family's website states (in reference to the Queen's Privy Council declarations of 1952 and 1960): "A proclamation on the Royal Family name by the reigning monarch is not statutory; unlike an Act of Parliament, it does not pass into the law of the land. Such a proclamation is not binding on succeeding reigning sovereigns, nor does it set a precedent which must be followed by reigning sovereigns who come after."
https://www.royal.uk/royal-family-name
Of course, the purpose of the statement is to emphasize that Charles (and his successors) can override the Queen's decision. But if her Privy Council declaration doesn't have the force of law, and the law allows a person to change their surname at will, could any of her other descendants also ignore her "will and pleasure" by adopting or rejecting the Mountbatten-Windsor surname for themselves?