This article investigates the International Criminal Court (ICC) as a law laboratory. Inspired by perspectives from the sociology of law, the article analyses how professional agents battled for control over the general direction and specific legal terminology of the Court, especially in its early life. Working also to distance the Court from what was perceived as excessive judicial creativity of the ad hoc international criminal tribunals for the former Yugoslavia and Rwanda, these agents created the conditions for a distinct laboratory of law in which new legal concepts and doctrines could be created. The article analyses in particular one new doctrine, the control theory based on Article 25(3) of the ICC Statute, as emblematic of battles to define the direction of the ICC as a law laboratory.