Present times are sometimes referred to as "the golden era of regulation", as more and more areas of social life are regulated. But regulation is not only increasing; it is also changing. New regulators are emerging, and they are issuing new kinds of rules. These new kinds of regulation are frequently not legally binding, and are therefore labelled soft regulation as opposed to hard law. It is not compulsory to follow soft rules but many actors - including sovereign states - still do, and the thesis asks the question why this is so. Why do even states, which are powerful regulators themselves, abide by soft regulation, and wherein lies the regulative power of soft rules?

Through an in-depth study of the European Union's pre-accession instrument Twinning an answer to the question of the power of soft regulation has been arrived at. Treating Twinning as a critical case of soft regulation, and using theories of imitation to grasp the meaning and evolution of Twinning projects, makes it possible to define three regulative elements involved in soft regulation. These are the combinative, co-productive and constitutive elements of soft regulation, from which the thesis suggests that it derives its power.

First of all, soft regulation combines different kinds of rules, the regulation of identity and the regulation of activity, and a variety of sources of legitimacy. Second, it depends on regulators and regulatees interacting to co-produce regulation. And third, as its main result, it constitutes the rule-followers as formal, rational, and modern organisations. Accordingly, soft regulation has rather impressive regulative capabilities, builds on complex, dynamic, and social interactions, and embodies as well as promotes some of Western society's most strongly institutionalised ideas. The thesis argues that it is through these characteristics that actors, including states, are compelled to follow soft rules.