This paper treats the design of judicial mechanisms (international courts, domestic courts, arbitral tribunals and the like) as variables that are intended to and do affect the output of these courts, particularly the scale and scope of claims about international law. It looks at the selection process for tribunal members, the terms of reference given the tribunal, and the post-adjudication retention constraints on members, such as length of term and non-reappointment. To test this claim, the paper focuses on six case histories of instances where judicial mechanisms have diverged about the content of international law, in some instances within a single overarching case. The case histories both illustrate and are consistent with four conjectures about the effect of variation in design on the content of the product of international adjudication: national courts will demonstrate great variation; the responsiveness of international tribunals to state interests will reflect these design features; regional tribunals will reflect particular regional interests to a greater extent than will broad-based multilateral tribunals; and special purpose tribunals will tend to expand their jurisdiction, which is the say the scope of the claims they make about international law, to a greater extent than will broad-based multilateral tribunals.