Succession is governed by the Acts of Union 1707 , which restates the provisions of the Act of Settlement 1701 , and the Bill of Rights 1689 . These laws originally restricted the succession to legitimate descendants of Sophia , Electress of Hanover ( the mother of George I ) , and bar those who are Roman Catholics or who have married Roman Catholics . The descendants of those who are debarred for being or marrying Roman Catholics , however , may still be eligible to succeed . By convention iterated in the preamble to the Statute of Westminster 1931 , the line of succession can not be altered in any realm without the assent of the parliaments of the other 15 realms , leading to the adoption of the Perth Agreement at the 22nd Commonwealth Heads of Government Meeting in October 2011
Commonwealth Heads of Government Meeting
Commonwealth Heads of Government Meeting 2011
Succession to the Crown Act 2015