The International Narcotics Control Board (INCB) has been severely criticized for its behavior since the early 1990s. Allegedly, its rhetoric and practice ignores scientific evidence, impedes policy development and is arbitrary. This paper analyzes the INCBs reactions to these allegations. The analysis shows that the INCB has reacted by taking some of the concerns gradually into account rhetorically and – to a lesser extent – also in practice. This result is surprising, because the INCB – as a quasi-judicial, independent body, whose practice is backed by powerful states – cannot be coerced in to changing its behavior. Theories on international organizations provide two explanations for the behavior of the INCB. First, based on principal-agent approaches, it can be argued that the INCBs behavior is a purely strategic. The INCB is buffering core tasks form external influence in order to maximize organizational autonomy. Gradual behavioral shields the INCB from being overturned by principals. Second, based on constructivist considerations, it can be argued that the INCB to restore its authority as a judicial body in international drug control. To remain an authority, it has to adjust to a changing normative environment. Gradual adaption is explained with a slowly changing organizational culture. Evidence does not allow excluding one of the two explanations. This is because distinguishing between behavior according to the logic of consequences and behavior according to the logic of appropriateness is not possible from a top-down perspective exclusively. How the critics perceived INCB’s behavior is equally important for understanding the legitimation strategies of the INCB.