Case C-402/18: Judgment of the Court (Fifth Chamber) of 27 November 2019 (request for a preliminary ruling from the Consiglio di Stato — Italy) — Tedeschi Srl, acting on its own account and as agent of a temporary association of undertakings, Consorzio Stabile Istant Service, acting on its own account and as principal of a temporary association of undertakings v C.M. Service Srl, Università degli Studi di Roma La Sapienza (Reference for a preliminary ruling — Articles 49 and 56 TFEU — Public procurement — Directive 2004/18/EC — Article 25 — Subcontracting — National legislation limiting the possibility of subcontracting to 30 % of the total amount of the contract and preventing the prices which apply to subcontracted services from being reduced by more than 20 % by comparison with the prices stipulated in the decision awarding the contract)