In the current emergency situation, national legislators attempt to manage the invariance in public procurements by means of analytical rules of mechanical application. The consequent regulatory chaos (in a continuous – almost inconsistent – reformulation of the rules) makes it preferable to manage the emergency through undetermined legal concepts (good faith, first of all), which better perform the homeostatic function in the legal system.

The paper analyzes the recent jurisprudence about prospective overruling on national administrative measures governed by EU law (Council of State judgment nos 17 e 18/2021) to test its compliance with ECJ’s jurisprudence. Indeed, it’s in the Court of Justice’s exclusive jurisdiction to determine if a declared violation of UE law may be tolerated for the time necessary to avoid the infringement of a legitimate expectation. So sentences of national judge about prospective overruling concerning EU law are ultra vires.

The withdrawal of unlawful acts of public administrations aids the judicial function to guarantee effet utile. It follows the functionalization of procedural autonomy to the principle of effectiveness of EU rules. This, however, cannot go against the Community principle of legal certainty and the protection of legitimate expectations. Hence, the conflict between certainty and justice must be resolved through a synthesis of the opposing interests by the application of the principle of proportionality which conforms to the principle of legality.