Within the scope of a treaty, a tax obligation only exists if and to the extent that, in addition to the domestic tax law requirements… Rules of double taxation are not, therefore, conflict rules (Kollisionsnormen) similar to those in private international law. Rather, they are «rules of limitation of law» (Grenznormen) <…> However, while such rules of limitation ordinarily are embodied in, or closely related to, the substantive rules of the domestic law of the state in question, the treaty rules are formulated separately from domestic tax law; they therefore have an independent origin and legal foundation.
Klaus Vogel, Double Tax Treaties and Their Interpretation. 4 Int'l Tax & Bus. Law. 1 (1986)
On one hand, double taxation conventions are international agreements entered into between governments for the allocation of fiscal jurisdictions. On the other hand, they become part of the tax law of each Contracting State, whether by direct incorporation into the domestic law or by enactment into that law.
Victor Uckmar. Double Taxation Conventions. In: Andrea Amatucci (ed.). International Tax Law (2006)
