The paper comments on the judgment of the EU Court of Justice (Grand Section) of 6 November 2018 (cases joined from C-622/16 P to C-624/16 P, Maria Montessori Elementary School/Commission) relating to the compatibility of the aid regulation State with the exemption of the municipal property tax (ICI) in reference to the properties used by ecclesiastical entities. With these rulings, the Court of Justice confirms its previous jurisprudence and at the same time introduces novelties of a certain importance which are highlighted. The European Court of Justice, for the first time, pronounces on the ex- istence of the conditions for the legitimation to act of private individuals who are placed in an unfavorable and distorted competitive situation, and only when the firm’s activity does not present character economic, the qualification of an enterprise can reasonably be denied with the consequence that any State aid granted to the firm can be considered compatible with the internal market. The Court also specifies what are the requirements that integrate an absolute impossibility of recovery of the aid granted and contrary to the unitary legislation.