El principio de proporcionalidad en el ámbito del derecho privado: una aproximación general y una particularización desde la óptica de la protección de los consumidores

The principle of proportionality, rooted in ideals of balance and reasonableness, is challenged at the legal level given its equivocal formulation. In public law, it is generally referred to as limiting the State’s discretion and protecting the rights of individuals through a threefold examination of adequacy, necessity, and proportionality in a strict sense. Such an analysis cannot be simply transferred to private law, either because it could end up eroding the logic of private autonomy, or because relations between private individuals cannot be qualified by the extent to which public policies affect fundamental rights. On the contrary, an evaluative weighing of the rights assigned to each party must be carried out, whether this exercise is done ex ante by the legislator, or ex post by the court. Hence, it is proposed that, unless there is an express or implicit redirection to the constitutional meaning of the principle, the balance between the rights of individuals must be observed in the light of criteria that are proper to private law, such as accepted good behavior (boni mores) and good faith. For these purposes, it is also postulated that in consumer law only a particularization of these rules can be observed, but this does not detract from the fact that their basis can be observed in other private law relationships, where there is a weakness of one of the parties, so that the principle of proportionality, based on ideas from the private law sphere, also serves as a corrective element.