Public policy is often implemented through formal laws. In contrast to the typically optimistic ex-ante analyses of the impact of a set of laws, in retrospect it may be hard to determine what the laws concretely produced. Particularly complicated to measure are the unintended and indirect effects on actors or values that were not the prime focus of the law. Despite the literature on these matters in other fields of research, among planners the theory of law implementation receives relatively little attention. This attitude may stem from the means-ends rationality that has been common to planning for so many years. This paper makes a plea for focusing on the interaction between people and laws so as to understand the outcomes. We do this by drawing insights from sociological perspectives on laws.