The resurgence of populism has highlighted the important role constitutional conventions play in a liberal democracy. Populist governments have frequently violated these conventions, in some cases as the first step towards a wider dismantling of the constitutional regime, while in other cases, the formal constitution remains intact while informal conventions continue to be widely flouted. Either way, there is a strong sense among liberals that there is something inherently objectionable about the violation of these conventions. This reflects a deep sense that conventions have legitimacy and should be respected by political elites. However, the legitimacy of conventions has rarely been explored. This paper addresses this gap, examining whether it is possible to develop a convincing theoretical account of the legitimacy of constitutional conventions. It argues that procedural accounts of legitimacy fail to provide a general foundation for the legitimacy of these rules, given that many constitutional conventions emerge as a result of long-standing practices rather than through a formal process of ratification. An account of legitimacy grounded in the idea of public reason holds more promise, although also has limitations given the extent of polarisation over core constitutional values. The paper instead proposes an account of convention legitimacy based on the idea of tacit consent, arguing this also highlights the need for greater public awareness of conventions.
