International Tax Law has developed in the last century mainly by means of a proliferation of double taxation agreements, which are signed by two Contracting States (and, therefore, bilateral) with the intention to limit their mutual exercise of tax sovereignty in order to avoid double taxation. It has been said that nowadays there are approximately 4,000 double taxation agreements signed bilaterally across the world, which explains that network being the center of the scientific debate in this field.
Despite this tradition of written bilateral norms, International Tax Law is also comprised by unwritten norms – such as the territoriality principle – and by soft law. In regarding of the latter, international organizations such as the United Nations (“UN”) and the Organization for Economic Cooperation and Development (“OECD”) have assumed an important role: first due to their technical capacity to formulate international tax policy; second, because specially OECD alongside with G20 – which has the political power that lacks to the first international organizations alone – are assuming a prominent role in proposing new tax rules to be implemented by national States in line with new international fiscal policies.
L.E. Schoueri & B.C.F.N. Santos. Pillar 2 and Global Tax Governance between. Anais do IX Congresso Brasileiro de Direito Tributário Internacional. IBDT. São Paulo: 2022.