For more than two centuries, the constituent assembly has been the classical way for government to begin again on a new ground of legitimation. However, in an age of democratic backsliding, new autocrats are hijacking the form of constituent assemblies without the slightest intention of generating public consent. We need a critical theory to assess when constituent assemblies do real legitimation work and when they are just covers for autocratic concentration. I show how our present theory is actually a theory of first constituent assemblies in a particular location. I propose that we use a different theory for assessing second and third and later constituent assemblies in a particular place. A later constituent assembly cannot displace an earlier one unless its democratic pedigree of the second is stronger than the first. Constitutional democracy embeds a normative one-way ratchet.