Constituent power in political liberalism: Constraining the future?

In Sovereignty across Generations, Ferrara attempts a dual feat. He demonstrates that political liberalism needs a nuanced doctrine of constituent power to be brought in line with traditional democratic concerns. At the same time, he argues that political liberalism is capable of making constituent power safe for democracy, in reining in its unruly and unbound character. By distinguishing between 'the people' and the electorate, Ferrara develops a transtemporal conception of the constituent subject, allowing moderate transformation but in effect binding all future time-slices of the people. In my comment, I address two issues with this. First, I ask how such accounts deal with the fact of immigration. It is not clear whether a historically indexed constituent subject has the normative power to bind new citizens arriving with quite distinct historical baggage. A second question is whether Ferrara's Rawlsian-Michelmanian take is different from, and superior to, the Habermasian account of constituent power, especially to Habermas's constructive views on supranational constitution-making. Both questions address whether Ferrara's historically indexed account is sufficiently open to future developments.