This article offers a new interpretation of one particular episode of Livy’s Gallic Sack narrative in Book 5 of the Ab urbe condita – i.e. of the constitutional challenge made by Marcus Furius Camillus to the Romano-Gallo ransom agreement (at 5.49.2). Camillus’ challenge to the constitutional validity of the ransom agreement on the basis of rank is first contextualised through other occasions when political decisions were made at Rome in the absence of the appropriate magistrate. On this basis it is argued that Camillus’ insistence on the constitutional invalidity of the agreement between Romans and Gauls is only one possible interpretation of what happened, and that, instead, it is equally possible to regard the ransom agreement as valid (and Camillus’ argument in consequence as invalid). The ambiguity between these two possible readings is then explained as a deliberate narratological strategy on the part of Livy to involve his readers in the ‘decision-making process’ concerning the constitutional validity of the Romano-Gallic ransom agreement. Whether or not Camillus was right, his constitutional argument emerges as a relic of a political culture of open public exchange and disagreement that was about to be lost forever at Rome.