Political liberalism, dualist democracy and the call to constituent power

Alessandro Ferrara's argument in Sovereignty Across Generations takes shape within a broadly Rawlsian 'political liberal' framework of thought about moral underpinnings for a constitutional-democratic practice of politics. Where, exactly (I ask here), is the place within that thought for concern about occurrences in a country's past of popular constituent power? If the country's currently established constitutional regime is fully democratic (and is otherwise morally in order) by whatever operational measures you and I might think to apply, why should we or anyone care about how or by whose authority the regime got set up and running in the first place? By Ferrara's Rawls-inspired teaching in Sovereignty Across Generations, the answer to that question will come from a certain conception of political legitimacy. But then a potent objection comes from those who press the question of how to reconcile a democratic conception of legitimacy with a subjection of current (say) deliberative-majoritarian rule to antecedently imposed terms of constraint. Under Rawlsian and Ferrarian stimulus, I look into the possible relevance here of H.L.A. Hart's proposition of a complementarity or fusion, in our concept of law, of an 'internal' with an 'external' perspective that those involved may adopt toward the coercive social practice in question. Underlying the Rawlsian constitutional proposition on legitimacy, I end by suggesting, is the thought that, in order for a person to live in freedom under law, that person will have to sustain simultaneously an internal attitude of bonding to their society's own ongoing project of legality and an external attitude of critical judgemental of that project as reasonably and rationally acceptable to free and equal citizens in conditions of reasonable pluralism.