This article examines treaty interpretation based on consensus, or the idea that legal or political practice that is not directly related to a treaty can be used in interpreting it, or at least in granting more discretion to States Parties. The practice of the Inter-American Court of Human Rights, contrasted with the well-settled practice of the European Court of Human Rights, reveals that consensus interpretation plays an important role in entrenching the legitimacy of international human rights courts. The Inter-American Court’s practice seems to rely on consensus when it supports a progressive, teleological interpretation of human rights. The article argues that this selective engagement eliminates the legitimacy-building possibilities of the consensus method of interpretation, but that the Inter-American Court, in seeking legitimacy not from States Parties, but other stakeholders, does not seem particularly concerned with legitimacy costs (even if it probably should).
