This volume contains contributions to a symposium of scholars from the Nagoya Law School and the Faculty of Law of the Albert-Ludwigs-Universität Freiburg on the topic "Reactive Instruments of Social Governance". Together with volume 20 of the Freiburger Rechtswissenschaftliche Abhandlungen it completes the documentation of the results of a joint research project funded by the Nagoya Institute of Advanced Research (IAR) and the Freiburg Institute for Advanced Studies (FRIAS). With the social governance by law and the interplay between substantive legal standards and procedural enforcement the symposium addressed a topic of both outstanding academic and practical importance. In the pursuit of certain political or social goals a legal system is basically faced with two options: the exertion of influence on the behaviour of its citizens by means of preventive or reactive instruments. The relationship of preventive and reactive regulatory instruments is a key element for the analysis and understanding of a legal system.