As modern constitutions bind democratic legislation to entrenched norms, they are in tension with the democratic idea that laws should be open to revision by new majorities. Against a widespread view, constitutional norms cannot be considered to be “more democratic” than ordinary laws due to specific qualities of the constitution-making process. Rather, the higher-level law of constitutions can fulfil a specific function as it may provide standards that ensure that laws made by the majority can be justified to everyone. On that basis, I evaluate for different types of constitutional norms whether there are good reasons for constraining legislation. In particular, entrenching cultural traditions and economic policy is more problematic than guarantees of the democratic process and rights ensuring respect for individuals. In sum, a two-tiered law-making system has important values, but people engaging in constitution-making and constitutional interpretation should be wary that the constitutional form is not abused.

This paper advances a functional analysis of the UK constitution. It explores how the UK constitution discharges three minimum ‘constituting’, ‘legitimating’ and ‘limiting’ functions that citizens living in modern liberal democracies may legitimately expect all constitutions – irrespective of form – to perform. This functional enquiry breaks with dominant trends in the legal scholarship that remain focused on theorising the constitution's underlying political or legal nature or, likewise, identifying its ultimate source of authority. In addition to offering a richer descriptive account of constitutional practice, this paper identifies, normatively, an institutional responsibility for Parliament to discharge the UK constitution's three minimum functions. Recognising that institutional responsibility unlocks fresh insights into two constitutional conundrums: the legitimacy of judicial review and the status of ‘constitutional statutes’. At the same time, it also exposes deficiencies and tensions in relation to the quality of Parliament's institutional performance on matters of minimum constitutional functioning.