If the study of positive law is to the jurist what fieldwork is to the sociologist, in the same way, domestic law is for the internationalist the raw material of his work. We sometimes tend to forget this, simply because private international law has its own objects of study, foremost among which are conflicts of law. The latter arise from a ‘founding antinomy’between, on the one hand, the division of the world into distinct legal orders since, as Niboyet pointed out, ‘each country must have a law adapted to its needs, and it is in diversity that true civilisation resides’and, on the other hand, the existence of international private relations.On the basis of this duality, private international law develops its own objectives, independent of domestic law, and sometimes contradictory: the coordination of legal orders, which is the basis of the conflict rule method,the true ‘medicine’ for conflicts of laws,and the preservation of their internal order, which is the basis of mechanisms derogating from the application of foreign law, so that international relations do not destabilise the social structure of state legal orders.The discipline draws its singularity from the pursuit of its aims through a methodological approach that can move away from domestic law, either because it leads to the multiplication of points of view that are foreign to it,or because it can be based on the structure of norms in order to deduce the appropriate method of resolution. Nevertheless, domestic law reappears, since the methods used have in common that they are based on its analysis in order to found the rule of jurisdiction or conflict on the legal centre of gravity of the relationship in question, according to the substantive considerations that it promotes.In other words, domestic law is primary in that it attempts to capture the raw fact giving rise to conflicts of law, and therefore constitutes the matrix of the conflict rules. This connection is particularly perceptible when the law of conflicts synthesises domestic law in order to constitute its own categoriesand to give legal institutions the appropriate international connecting factor. In so doing, it casts an original eye on the legislative bodies in question, often revealing their deficiencies.It is on this double exercise of synthesis and characterisation, on the one hand, and of connection, on the other hand, that the present thesis focuses in a field, financial law, where the method of the rule of conflict has not lost its vigour.