Can informal judicial norms protect against political pressure?

International tribunals are pulled between a commitment to judicial autonomy and the need to manage their members’ political expectations, lest these rein in the tribunal’s power. We argue that when the formal design of international institutions leaves them exposed to political control, institutional actors can respond by self-imposing constraints to protect themselves from excessive oversight. We examine this phenomenon in the context of the World Trade Organization’s (WTO) Appellate Body (AB), touted until recently as one of the most successful international tribunals in existence. We argue that the early insistence on collegiality and consensus opinions among WTO AB members had the effect of (i) deflecting political blame and (ii) providing cover for adjudicators who did not dissent when governments might have wished them to. As the informal norm of consensus opinion was weakened, political control by WTO members grew stronger, culminating in the United States’s move to paralyze the AB. Weaker actors can thus improve their position under formal rules, yet this requires a strong commitment to a set of informal norms, which comes with its own challenges.