The case is one of the recent and of the benchmarks of the Court of Justice of the European Union (hereinafter referred to as: CJEU) that was followed by intense political debates, high-level legal argumentation, and expectations based on the national competences and the equal treatment from both – Austrian and German – sides, all across the European Union (hereinafter referred to as: EU).The case is a landmark one from several aspects. First, this is an infringementprocedure, the rarer version when a Member State (hereinafter referred to as: MS) sues1 anotherMSforthebreachofobligationsarisingfromEUlaw. Secondly,the case is uniquefrom the point of differences in the opinion of Advocate General Nils Wahl and the reasoning of the CJEU. Thirdly, the judgement might be categorized as a borderline case of collision. Both the AG and the CJEU had to examine the EU competences in the light of the principle of subsidiarity declared in Article 5(3) of the Treaty on European Union (TEU) and Protocol (No 2) on the application of subsidiarity and proportionality regarding the tax- sovereignty of the MSs. The reasoning of the AG and the CJEU is altering and in a significant sense. This difference highlights the values of scientific reasoning and perspective and the pragmatic one. Both argumentations are convincing besides being controversial. AG Wahl applied a clear scientific analysis wrapped in wise reasoning. The CJEU has solved the case by following a pragmatic aspect, using the discriminatory- reference as a Trump-card of constituting the legal base, which usually overwrites national interests. Last, but not least, the decision – arising from the abovementioned significances – is a newborn textbook example for the creeping extension of Union competences, too. Within the frames of this paper, we emphasize the different perspectives of the AG and the Court. This paper aims to present the importance of uniform legal interpretation, especially in today's innovative societies. The European Union intends to modernize the integration from a technological and a legal point, too. The objective is to reach social welfare and economic progress within a modern and quite flexible legal system of harmonized rules and a well-functioning internal market. The guarantee for the well-functioning (border- and obstacle-less) internal market is on the one hand, the adequate share of competences between the EU and the MSs.On the other hand, the provision of equal treatment to the nationals of other MSs who intend to live cross-border lifestyles and by this, to accomplish the market in practice. Thus, it is not that simple to cross the appropriate line between the sovereignty and competences of a state and its obligation for equal treatment (which means non-discrimination in practice). The field of taxation belongs to MSs competence. However, the MSs shall ensure equal treatment in all circumstances and this is the edge of the room-maneuver for the freedom of the MSs to exercise their full powers with full power. Besides, the CJEU has already started to slowly, creepingly extend its competences regarding the interpretation of EU law. By the unique interpretation, the Court fills the legal acts with content and is able to (trans)form law, not just the Common European Law, but also – by having an indirect impact – the national laws, too. This is called, the creeping extension of Union competences. We find it significant to examine the differences of the reasoning of the AG and the Court which could be found in the perspective and methodology. Since the CJEU has maybe the most relevant role in the transformation of European law and its tendencies, it might be interesting to see how the Court forms the law. In the case of Austria v Germany, the controversial argumentation of the relevant actors is very thoughtful. Well, does the case provide the main rule or an extraordinary exception that proves the rule?
