What is the role of law in a society in which order is maintained mostly through social norms? In Law and Social Norms, Eric Posner argues that social norms are sometimes desirable yet sometimes odious, and that the law is critical to enhancing good social norms and undermining bad ones. He argues that law and social norms are closely related, although their connection may be hard to see. The proper regulation of such norms, he notes, is a delicate and complex task.

Posner adheres to a theory of law that takes a cost-benefit or economic approach to law. Critics of this approach argue that it requires superhuman information-processing capabilities. The economist's response, with which Posner agrees, is that the various parameters should be taken into account even if they cannot always be taken into account with precision. In this book Posner applies the economic approach to social norms.

The recent literature in law and economics on social norms focuses on two issues: the conditions under which norms should be expected to be efficient, and the attitude that the state should take toward norms. A related issue concerns the extent to which courts should defer to attempts by groups to resolve disputes with nonlegal means.

The concept of a "norm" is slippery. For Posner, it is a rule that distinguishes desirable and undesirable behavior and gives a third party the authority to punish a person who engages in the undesirable behavior. In this way, a norm is like a law, except that a private person sanctions the violator of a norm, whereas a state actor sanctions the violator of a law. A norm is a rule that governs collective behavior and that is enforced nonlegally. An illustration of a norm is that of keeping one's place in a line. Another is a criminal gang's norm of loyalty. At one time, until outlawed, the norm of dueling prevailed in many groups.

Posner discusses a number of areas of law, each in a separate chapter, that involve the regulation of social norms: gifts and gratuitous promises; family law; voting, political participation, and symbolic behavior; racial discrimination and nationalism; and contract law and commercial behavior.

The courts, he points out, "must evaluate the stigmatizing effect of an action, the conformity of behavior with social norms, the meaning of symbols, and the consequences of ostracism." Does the stigmatizing of AIDS patients or the publication of a sex offender's record as required by Megan's Law enhance social norms that constitute public order? Does affirmative action enhance the stigma of belonging to a minority group or weaken such stigma? "Modern social welfare and bankruptcy legislation," he notes, "was intended to eliminate the stigma against people who are poor and cannot pay their debts, . . . yet earlier versions of such legislation were intended to strengthen the stigma. Expungement laws, which erase criminal convictions from offenders' records, reduce the stigma of the ex-convict."

Privacy is not a theme much stressed in the book, although its connection to the subject might seem obvious. To say that a person values privacy is to say that he fears the enforcement of social norms. The steady increase in the commitment to privacy over the past century is linked to the decline of community and the rise of the rule of law. A person's concern for his privacy is not just a concern about concealing discreditable or embarrassing information about himself; it is a concern about protecting himself from being shunned because of his failure, currently or in the past, to conform.

Another trend is the decreasing protection of reputation under defamation law. The Supreme Court has weakened the common law of defamation by its endorsement of the free speech clause of the Constitution. The consequence is that reputation has become a less valuable asset than it used to be. As the author states, "If people can call me a liar and escape legal retaliation, then I do not have much incentive not to lie; after all, whether I lie or not, the accusation might stick."

Five of the chapters in the book are revised versions of articles that have appeared in law reviews. Each of the chapters can be read independently of the others. The result is that while the volume has a general theme, it is something of a hodgepodge. The book has interesting ideas, but on the whole it is not an easy read.

Dr. Slovenko is professor of law and psychiatry at Wayne State University School of Law in Detroit.