One of HLA Hart’s main contributions to jurisprudence is his theory of social rules. Hart claimed that a social rule has an external, behavioural aspect, and an internal, attitudinal aspect. However, Hart’s description of the internal aspect of social rules left much to be desired. Drawing on recent work in the philosophy of action, I argue that the internal aspect of social rules is best thought of as the widespread ‘acceptance’ that an action should be performed. The technical notion of acceptance I rely on is related to Hart’s own understanding of acceptance, but the two differ in several important respects.