In the Engie case, the Tribunal held that the issuance of a tax interpretation contrary to national law could create inadmissible state aid under EU law. Both Engie and Luxembourg challenged the judgment before the CJEU, pointing, inter alia, to an error in the Tribunal's understanding of Luxembourg law.
Advocate General Juliane Kokott, in her opinion in case C-451/21 P, argues that not every factually erroneous position of a national tax authority will create prohibited state aid. This will only be the case if there is a clear contradiction with national law and, at the same time, it is a deliberate action by the state authorities aimed at granting state aid.
The article endorses this position.