The prime minister's constitution: Cabinet rulebooks in Westminster democracies

The transformation of governance in Westminster democracies is well documented. However, one aspect of their change that has not received much attention is the creation and publication of cabinet rulebooks. The few studies of cabinet rulebooks have focused on their potential constitutional implications, leaving unclear how their emergence fits within the broader development of Westminster governance. We address this gap in the literature by examining cabinet rulebooks in five Westminster democracies: Australia, Canada, Ireland, New Zealand, and the United Kingdom. We analyze their features and emergence, and then set out a framework to analyze their potential effects on cabinet dynamics. We find that the appearance of cabinet rulebooks can be tied to several forces of change in Westminster systems, but most especially the growth of government. Furthermore, we find that these rulebooks project an account of prime ministerial power that is favorable to the prime minister.