This note uses a new data set on international territorial disputes and boundary agreements to explore whether and how legal commitments affect state behavior. Do border treaties reduce subsequent conflict simply through their effect on the distribution of the disputed good, or do treaties have legal and political implications such that a given distribution of territory has different effects depending on whether it is de facto or de jure? There are three main results. First, among states that have homeland territory disputes, the adoption of a legally binding border is associated with a significant reduction in the likelihood of future militarized conflict over the territory. Second, this effect is the same regardless of whether the treaty transfers territory or converts a de facto or contested border into a de jure border without changing the status quo distribution. Third, there is no equivalent reduction in conflict when states create explicitly provisional borders that allow them to retain their claims to areas that they do not possess. These findings suggest that border treaties do more than simply specify the distribution of territory and provide for transfers. By requiring states to renounce claims to territories that they do not receive, treaties generate ex ante costs of signing and/or ex post costs for reneging that explain their association with subsequent peace.