My second reason is not less important. The power of law to define modes of social conduct depends very largely upon its ability to command a sentiment of general approval. What it seeks to do must broadly commend itself, on rational grounds, to those over whose lives its principles are to preside. Legislation which does not fulfil this condition is always unsuccessful, and always has the result of bringing the idea of law itself into contempt. For where a particular statute is regarded as foolish or obnoxious by a considerable body of persons, they will rejoice in breaking it. Illegal conduct becomes a matter even of pride. It becomes a principle of conduct which gives rise to special pleasure and peculiarly satisfies human vanity. No one in London, so far as I know, regards the average policeman as an unwarrantable attack on liberty; but it seems to be the case that thousands of people in New York regard the prohibition agent in that way. They wear a breach of the law as a badge of courage, like the revolutionary in Czarist Russia or the suffragette in pre-war England; and the imposition of penalties upon them arouses in them and their friends a sense of angry injustice. Now I think it is an elementary principle of penal psychology that you cannot make a crime of conduct which people do not _a priori_ regard as criminal. Popular sentiment approves a law against murder, and you can enforce that law. But popular sentiment, in England at least, would not, in my judgment, approve a law forbidding the manufacture and sale of alcoholic liquor; and its chief result would be to direct the minds of thousands to the problem of ways and means of evading the law. That is a habit which grows upon those who indulge in it. It loosens all the principles of conduct which make for social peace by making us think of the rules under which we live as unjustifiable and oppressive. It forces social effort quite unduly and unwisely in one direction. It persuades it to think out mean and petty expedients for the enforcement of the law in the same way as its subjects think out mean and petty expedients for its evasion. The spectacle, for instance, of the Supreme Court deciding that the American government is entitled to tap telephone wires in order to obtain evidence of infraction of the Volstead Act is not an encouraging one.[39] That way lies corruption and blackmail, the kind of habits which, in England, we associate with names like that of Oliver the spy,[40] in Russia with that of agents-provocateurs like Azeff. Few things are more detrimental than this to the moral equilibrium of a social order.