I have covered a great deal of territory, and it will be useful to conclude by recapitulating the principal themes.
It is pointless to raise ethical objections to nudges and choice architecture as such. Human beings cannot live in a world without them. Social norms nudge, and a society cannot exist without social norms. Many such norms make life agreeable and even possible. They increase the likelihood that people will not abuse or mistreat one another, and they help solve collective action problems that would otherwise make human lives shorter, sadder, and worse. Such norms influence us every day, even when we do not notice them. They can emerge without any involvement from political actors, but the law has an expressive function, and what it expresses influences the content of norms. If a state takes violence seriously, and attempts to stop it, it can fortify norms against violence. And if a state takes steps to reduce discrimination on the basis of race, religion, sex, and sexual orientation, it will influence norms. Healthy behavior, including good diet and the avoidance of cigarettes and alcohol, is very much a product of choice architecture, emphatically including social norms.
Spontaneous orders have many virtues, but they nudge. Whether or not they are associated with liberty, properly conceived, they create multiple forms of choice architecture. Some people celebrate small groups, informality, and longstanding traditions that seem to have nothing to do with government. Other people deplore such groups and traditions. But whether they deserve celebration or something else, they produce choice architecture. The most minimal state creates such an architecture, and it will influence people's decisions even if it seeks not to do so. Recall the effects of default rules, of the sort that are pervasive in the law of property, contract, and tort. But while nudging itself is inevitable, many nudges are anything but that, and they can be avoided. Some forms of influence are not the appropriate business of public officials.
The modern regulatory state imposes numerous mandates and bans. Some of them are easily justified, as ways to solve collective action problems, to reduce externalities, or to response to people's lack of information. But some forms of coercion must be characterized as paternalistic.