Estlund’s Democratic Authority makes much of the idea of acceptability requirements for political justification. Acceptability requirements come in different versions, and one respect in which those versions can differ is what they are requirements for. They might be requirements for laws, policies, procedures, constitutional structures, the kinds of reasons that citizens or certain officials can give in certain public fora, and so on; they might also require acceptability as a condition for justification quite broadly, for political or legal authority more narrowly, or for political legitimacy — i.e., the moral permissibility of a government’s enforcement of its laws by coercive or punitive means. For Estlund, as for many, the most important application of acceptability requirements is to legitimacy, since coercion raises peculiarly urgent questions of justification. The rough idea of an acceptability requirement on legitimacy is that laws backed by coercion must be acceptable to the citizens that they purport to govern, and must be acceptable to them despite their deep moral, religious, and philosophical disagreements.
Discussing the views of Joshua Cohen, Estlund writes:
For Cohen the fundamental tenet of a deliberative account of democratic legitimacy is the principle that coercive political arrangements and decisions are morally illegitimate unless they can be justified in terms that can be accepted by citizens with the wide range of reasonable moral, religious, and philosophical views likely to emerge in any free society. (Democratic Authority, 91)
Earlier in the book, Estlund cites Rawls describing what he calls the “liberal principle of legitimacy”: