I would like to highlight a great book, recently published, by Richard H. McAdams from Chicago Law School on the Expressive powers of Law. (Harvard University press 2015)
The book brings together lots of research, which has been carried out throughout the years by McAdams and his co-authors on this important topic. McAdams, one of the most important scholars in this tradition, was among the first legal scholars to recognize that law can affect behavior not only through sanctions and morality.
I personally feel especially connected to the expressive function of the law since I have written my mostly experimental dissertation on this topic. What’s unique about the subject is that it captures something which many people feel lies somewhere between deterrence and moral/fairness based approaches to compliance but it is actually based on both. This approach is also unique in a sense that it represents research conducted by people from different disciplines, each suggesting a different account for what expressive law really captures. For example, one of my PhD advisors, Bob Cooter, has developed a competing thesis to this topic. This concept has attracted scholars in the field of law and philosophy to write about it and people who focus on law and institutions have worked on it as well.
The specific thesis provided by McAdams focuses on the notion of information provided by the law as a way to help people coordinate their action. Clearly, the focus on information signaling and focal points brings to the table, something which is distinctively different than deterrence or internalization. Interestingly, while McAdams himself is mostly a Law and Economics scholar, he does review many of the relevant literatures from various other disciplines and analyses them.
However, at the same time it is clear that law serves as a much better focal point when it is seen as something that might be obeyed due to either extrinsic or intrinsic rationales. This is why it is important to recognize that this third "in between" type of effect of the law captures parts of the more traditional approach to the effect of law on behavior.
McAdams' book is also very interesting in a world where states now communicate with citizens through nudging them by various situational cues, which are sometimes beyond their awareness. Revisiting some of the more traditional effects of the law, when people are aware of the effects of it and can deliberate on its meaning, is therefore a highly needed task.