Do international court judgments influence the behavior of actors other than the parties to a dispute? Are international courts agents of policy change or do their judgments merely reflect evolving social and political trends? We develop a theory that specifies the conditions under which international courts can use their interpretive discretion to have system-wide effects. We examine the theory in the context of European Court of Human Rights (ECtHR) rulings on lesbian, gay, bisexual, and transgender (LGBT) issues by creating a new data set that matches these rulings with laws in all Council of Europe (CoE) member states. We also collect data on LGBT policies unaffected by ECtHR judgments to control for the confounding effect of evolving trends in national policies. We find that ECtHR judgments against one country substantially increase the probability of national-level policy change across Europe. The marginal effects of the judgments are especially high where public acceptance of sexual minorities is low, but where national courts can rely on ECtHR precedents to invalidate domestic laws or where the government in power is not ideologically opposed to LGBT equality. We conclude by exploring the implications of our findings for other international courts.