The account of punishment in De iure belli ac pacis develops most fully the relationship Grotius understands between strict rights and those claims arising from dignity or merit, which he associates with ‘expletive’ and ‘attributive’ standards of justice, respectively. The purpose of this article is to provide a philosophical reconstruction of two particular puzzles that arise out of the role Grotius assigns to the concepts of right and merit in the theory of punishment. How, in the first place, can a right to punish be legitimated if not on the grounds that the offender merits punishment for the crime? And then, if merit does not provide the grounds for punishment, why must the penalty be strictly limited to what the offender merits? A reconstruction of Grotius’s arguments grounding the right to punish and justifying the role of penal merit brings out the underlying coherence in Grotius’s theory of punishment, while also revealing that the norms of expletive and attributive justice are inextricably linked in Grotius’s system of natural right.