European tax law essentially comprises Community law and the Europeanized national tax law of the EU states. This is unprecedented and has no essential links to theories of international law. It presents itself as law sui generis, with an interlocking of the legal and constitutional orders of sovereign states.
At the same time, the tax systems in Europe are relevant that affect countries that do not or not yet belong to the EU, e.g. B. Norway, Switzerland. The entire external tax relations of the EU to the so-called third countries are hardly the subject of studies. The focus is on community law and the Europeanized tax law (Europeanization) of all EU countries (see individual states).
The ECJ is playing a key role in the current process. It also includes overriding principles in its jurisprudence. Primary law and secondary law must be assessed between convergence and divergence, between point harmonization and subsidiarity.