This article offers a critical discussion of two influential positions in contemporary legal and political theory, which will be referred to as ‘political constitutionalism’ and ‘strong popular sovereignty’. Despite their important differences, both share a sceptical approach to the dominant constitutional practice in liberal democracies, hence they are brought together here under the term ‘weak constitutionalism’. They both highlight the political dimension of the constitution, arguing that democratic legitimacy requires institutional arrangements that give the people and/or their representatives the last word in settling fundamental issues of political morality. By contrast, this article underlines the legal dimension of the constitution as the repository of the moral principles that make possible a practice of public justification in constitutional states. It is from this second constitutional dimension that the critical arguments are developed, both against the desire to take the constitution away from the courts and the aspiration to recognize the constituent power as pre-legal constitution-making faculty.