The article aims to deepen the role of comparison in the famous Institutes of Gaius, by asking what were the objectives of the use of this instrument by Gaius himself. First of all, this article will highlight the methods and the interpretation that derived from its application by the jurists of ancient Rome and explore the reasons why the comparative method was little used and distrusted in Roman jurisprudence. We will then analyze Gaius' use of the comparative method with respect to some specific foreign norms in order to explain and understand certain legal situations. In particular, it is necessary to highlight the institute of tutela mulierum through which, by comparing it with other foreign norms, Gaius casts doubt on its effectiveness. Thus, the figure of Gaius as a critic of law emerges, in addition to his already well-known figure as a teacher and historian. We can finally come to the conclusion that Gaius does not wish to make changes to the Roman legal system, the traditional legal system par excellence, but rather to explain, through the use of foreign law, the complexity of the Roman legal system.