If it is the case that it is never society as a whole which acts in these matters to protect itself- that is, its members- but a small group of people who have acquired the power to tell society what to do (whether or not they claim to act on behalf of and for the good of that society), then the only a priori legitimacy they can claim for restricting the freedom of others (if indeed they feel the need to justify themselves at all) is the net good that the constraints bring about.
The more I think about this, the more I realise that my point of view owes at least as much to practical considerations derived from empirical observations of the effects of legislation as to the first principles of moral philosophy (perhaps if I knew what the first principles of moral philosophy were I might try to apply them).
It becomes necessary, therefore, to look at the practical effects of such constraints and prohibitions. Not that politicians are much interested in this kind of thing; after all, one dead child in the Daily Mail carries more weight at Westminster than all the freedom in the world. But it gives us a chance to anchor all the theory in reality.
It is common knowledge that the prohibition of alcohol in the United States was largely ineffective in terms of its own stated aims, and socially calamitous in terms of the crime and economic damage it inflicted on the country. It is generally accepted that the long term, international prohibition on many narcotics has resulted in vast human misery and organized violence on a massive scale, while only having a small effect on the consumption of these substances. Widening the scope, prohibitions on gambling led not to an absence of gambling but to colourful characters in pubs and down alleys. Attempts to eradicate homosexuality in Iran have led only to numbers of young men swinging from cranes. Attempt to prohibit fun in Afghanistan have led to more wedding parties being gunned down by terrorists who feel they have right on their side. The urge to control at all costs can do far more damage to society than freedom ever has.
Unfortunately, common knowledge it may be, but it isn’t easy to pin down the facts. There are many reports and analyses of Prohibition, and some conclude that it did reduce the problems caused by alcohol, and that the crime associated with the period was not a direct result of the law.
In practice, it’s all terribly complicated. But in theory, I’m right.