An appeal to the Court of Cassation (against a decision of the Council of State) for reasons of jurisdiction can never concern a principle of law, even if this principle is stated in an interpretive ruling issued by the Council of State. The 'nomophylactic role' attributed to the plenary session of the Council of State (i.e. its exclusive role in the interpretation of the substantive and procedural rules which it applies), is a safeguard of the balance between the two jurisdictions (ordinary and administrative) that is enshrined in the Italian Constitution.