This paper begins with the observation that, when deciding on a course of action for themselves and their states, individuals sometimes take international law into account, and it sometimes serves for them a reason or a ground for action. It consequently asks why international law would serve as a reason or a ground for action, and whether there is anything international law could do to further encourage people’s consideration of it. The paper proposes a theoretical model which aims to account for those instances in which international law seems to exert a “compliance pull” on individual people. The model suggests there are two types of allegiance to a legal system: a person’s disposition to comply with legal rules, and a person’s fidelity to the system. A legal system's adherence to principles of legality is important for the generation and maintenance of both.