The most prominent method to interpret modern law is teleological. It assumes that legal rules serve a discernible purpose. We focus on one frequent purpose: the law helps the citizens overcome a dilemma. Illustrations comprise the environment, privacy, innovation, or competition. One line of our research aims at reconstructing such policy problems, and testing to which degree legal intervention is a precondition for solving them. A second line of research investigates in which ways and how successful legal rules change the behavior of the law's subjects. The third line aims at understanding the process in which new rules are made, and existing rules are applied. Most of our work is experimental. Lawyers and behavioral economists closely collaborate.