Laws attract certain types of discussion, interesting but wearingly familiar: authority and obedience, solemnity, legitimacy, coherence, utility, etc. But if you can put these things aside and consider only a law’s bare import, then you’ve freed yourself to consider how that bare import harmonizes, challenges, and reacts with the existing norms of a community. This is the expressive function of law. It is the child of the University of Chicago and now a mature field of study, which Prof McGinn presents and dissects with both approval and reservations. His ultimate aim is to offer an illustration from Roman law, i.e., to consider the effects of certain Roman legal institutions, evaluated not as solemn commands but as efforts to change or reinforce the social meaning of certain behavior.

Now if you’re new to Roman law you’re probably trying to imagine the expressive function of the Tarpeian Rock or Nero’s human torches, but Prof McGinn has found a gentler (and more instructive) example: the lex imperfecta. This is a somewhat uncertain category of statute that announces the lawgiver’s expectations without attempting to void the underlying prohibited act, or prescribing a penalty for disobedience. It is, in short, the perfect vehicle for considering, and perhaps measuring, the effect of a law sent out (to all appearances) weaponless into the Roman arena.