The law is humanity’s most important system to guide and correct human conduct. It is the key system we have to respond to deviant and criminal behavior, whether amongst adults or youth. There is now a large body of scientific work that could guide our laws to be more effective in preventing and reducing misbehaviour. However, so far this body of work has only had limited impact in both the professional legal sphere where laws are designed and operated and the broader public debates about criminal justice. This talk will present some key insights about when law does and does not effectively help to reduce and prevent harmful and damaging behavior. It will discuss what these insights mean for ongoing debates about criminal justice reform. It will discuss how behavioral science could play a larger role towards a preventive form of criminal justice that is evidence based in design and practice.