Public decision making is increasingly facing conditions of uncertainty, especially if analyzed under a governance perspective. The law tends to look at decisions under uncertainty as an exception from decisions under certainty. However, so far the legal prerequisites for decisions under uncertainty and their monitoring have been little researched. Indra Spiecker has developed a theory, that does justice to the specific features of decisions under uncertainty and assures their constitutional legality. She employs an intra-disciplinary approach, including insights from neighboring sciences such as economy and behavioral sciences. This approach stresses the importance of the preparation of decision making, such as the collection and transfer of information and its end. Rules of uncertainty can guide public decisions makers in the evaluation of a lack of knowledge as a risk or a chance. Consequently, control norms change. The principle of proportionality in particular gains a new and increased importance. The author shows that strengthening the importance of procedure and the application of the uncertainty rules enables effective control under changing conditions of uncertainty.