The following article attempts to dismantle the assumptions that the vertical comparative methods, especially those using a bottom-up approach, from national to international level, are surrounded by intricacies related to the internalization of international norms, in the context in which the contemporary administrative and legislative measures tend to be divided into two categories: (a) those related to the State’s economic intervention (public policy of direction) and (b) those pertaining to the protective and anticipatory legal intervention (public policy of protection). The fundamental issue that needs to be addressed is whether it is possible to refine the concept of longitudinal comparative approach, correlated to the intrinsic elements of traverse comparative approaches of contemporary Consumer Law.Furthermore, there is a contrast to be marked between longitudinal comparison, based on analogies which are made between legal systems of the past, in order to extract essential features valuable in the approaching of contemporary legal order and, in an antagonistic manner, the traverse comparative approach of Consumer Law which valorises the main trends of contemporary legal orders, while simultaneously approaching features from several contemporary legal systems. Several studies have been focusing on the problematic of horizontal/vertical comparative methodology, as well as to the intricacies characterizing the longitudinal/traverse comparative approaches of Consumer Law; nevertheless, there is space left for investigating the extent to which vertical comparative methodology represent an adequate means to deliver accurate information on legal transplants and conceptual trends in national legal orders related to the number of the compared legal systems, both from the angle of bilateral comparative law, while the comparison is carried out as a dichotomy of two legal systems, as well as from the perspective of multilateral comparative law, when the comparison takes place between more than two legal systems, using a variable-oriented approach. As an explanatory example of vertical comparative approaches of Consumer Law, we will use the comparative analyses at national level on the judicial meaning of the notion of mandatory rules and the various degrees in the extent to which a mandatory rule must be applied through the means of consumer legal protection. Secondly, vertical comparative approaches are also helpful in investigating the national ‘absorption’ of specific regulations on the professionals’ pre-contractual liability, which takes shape in all the cases where the professional – consumer relationship implies the duty of transparency.

Keywords: vertical comparison; horizontal comparison; longitudinal comparative approach; traverse comparative approach; Consumer Law.