I think the main problem with Mayor Bloomberg’s ban on gigantic sodas in NYC is that it won’t work. If obesity was mainly caused by this one product, perhaps you could make a case. If it led directly to saving lives like, say, mandatory seat belts, sure, that would make sense. But Bloomberg’s ban lacks such precision. 

Other people think that the main problem with Bloomberg’s plan is that he’s trying to create a nanny state, that’s he’s using state-sanctioned moral suasion. But is that always wrong: From Cass R. Sunstein’s New York Review of Books piece about Sarah Conly’s book Against Autonomy: Justifying Coercive Paternalism:

“Many Americans abhor paternalism. They think that people should be able to go their own way, even if they end up in a ditch. When they run risks, even foolish ones, it isn’t anybody’s business that they do. In this respect, a significant strand in American culture appears to endorse the central argument of John Stuart Mill’s On Liberty. In his great essay, Mill insisted that as a general rule, government cannot legitimately coerce people if its only goal is to protect people from themselves. Mill contended that

the only purpose for which power can be rightfully exercised over any member of a civilized community, against his will, is to prevent harm to others. His own good, either physical or mental, is not a sufficient warrant. He cannot rightfully be compelled to do or forbear because it will be better for him to do so, because it will make him happier, because, in the opinion of others, to do so would be wise, or even right.

A lot of Americans agree. In recent decades, intense controversies have erupted over apparently sensible (and lifesaving) laws requiring people to buckle their seatbelts. When states require motorcyclists to wear helmets, numerous people object. The United States is facing a series of serious disputes about the boundaries of paternalism. The most obvious example is the ‘individual mandate’ in the Affordable Care Act, upheld by the Supreme Court by a 5–4 vote, but still opposed by many critics, who seek to portray it as a form of unacceptable paternalism. There are related controversies over anti-smoking initiatives and the ‘food police,’ allegedly responsible for recent efforts to reduce the risks associated with obesity and unhealthy eating, including nutrition guidelines for school lunches.

Mill offered a number of independent justifications for his famous harm principle, but one of his most important claims is that individuals are in the best position to know what is good for them. In Mill’s view, the problem with outsiders, including government officials, is that they lack the necessary information. Mill insists that the individual ‘is the person most interested in his own well-being,’ and the ‘ordinary man or woman has means of knowledge immeasurably surpassing those that can be possessed by any one else.’

When society seeks to overrule the individual’s judgment, Mill wrote, it does so on the basis of ‘general presumptions,’ and these ‘may be altogether wrong, and even if right, are as likely as not to be misapplied to individual cases.’ If the goal is to ensure that people’s lives go well, Mill contends that the best solution is for public officials to allow people to find their own path. Here, then, is an enduring argument, instrumental in character, on behalf of free markets and free choice in countless situations, including those in which human beings choose to run risks that may not turn out so well.

Mill’s claim has a great deal of intuitive appeal. But is it right?”