The 16 countries that have Queen Elizabeth as their monarchagreed to the changes put forward by British Prime Minister David Cameron, who had called the rules of succession outdated.
“The idea that a younger son should become monarch instead of an elder daughter simply because he is a man, or that a future monarch can marry someone of any faith except a Catholic, this way of thinking is at odds with the modern countries that we’ve all become,” Cameron told reporters.
The agreement came on the sidelines of a Commonwealth summit presided over by the Queen in the remote west Australian city of Perth.
Current succession rules dating back to 1688 and 1700 were designed to ensure a Protestant monarchy, and bar anyone in line to the throne from marrying a Catholic.
Only a Catholic link is barred. There are no restrictions on marrying members of other religions or atheists.
The rules have their roots in a turbulent period of English history dating back to Henry VIII’s break with Rome in the mid- 16th century. The laws were imposed at a time when Catholics were seen as a threat to the state.
However, the British monarch remains head of the Church of England.
The leaders also agreed to drop the practice of giving precedence to male over female heirs to the throne, regardless of age.
The issue has been brought into focus by this year’s wedding of Prince William, second-in-line to the throne, and Kate Middleton.
Without a change, their first son would eventually become king even if he had an older sister.
A group will now be set up to coordinate the necessary legislation for the changes.