The text reproduces the keynote address, delivered by the author at an event marking the national Constitutionality Day, held on 18 December 2025 at the Constitutional Court of Slovenia in Ljubljana. The address reflects on the principles of rule of law, equality before the law and respect for international law as some of the key values enshrined in the Slovenian Constitution. The first part discusses the development and achievements in international criminal law over the past 80 years, focusing on three key aspects: institution-building, the growing importance of domestic prosecution and adjudication of international crimes and strengthened efforts at codification. It then turns to the challenges faced by international criminal courts and tribunals and international law more generally. The author discusses the unprecedented attacks and political pressure directed at the judges of the International Criminal Court and notes that judicial independence is a cornerstone of the rule of law and should be vigorously defended. International law, regional human rights instruments and the Constitution are complementary building blocks of the rule of law at both national and international levels. Strong and independent domestic courts strengthen international justice, whilst strong and independent international courts strengthen rule of law at the national level.

Key words: Constitution of the Republic of Slovenia, international law, international criminal law, international courts and tribunals, International Criminal Court, Nuremberg Trials, rule of law, judicial independence, codification of international law, international crimes.

If the addressee does not live at the address used for service and has no ongoing contact with it, service at that address will be merely fictitious, regardless of whether it is an officially registered address. Some national laws (notably in the Czech Republic) permit such ‘fictitious service’ at the outset, whereas most EU Member States require a genuine attempt to ascertain the individual’s actual place of residence first. The European Court of Human Rights and the Court of Justice of the European Union have articulated broadly comparable standards. EU Regulation 2020/1784 nevertheless raises practical difficulties. It encourages cross-border address searches, yet relies primarily on official registers. This is approach works where the information collected from these registers corresponds to the actual residence of the addressee. However, if this is not the case, service at the registered address would be merely fictitious. This is only in accordance with the requirements of a fair trial only where all reasonable attempts to determine the addressee’s actual address have been exhausted.

Key words: right to be heard, principle of proportionality, fictitious service, registered address, unknown address.

The Constitution of the Republic of Slovenia prohibits retroactive legal effect of statutes and provides four cumulative conditions that must be met for retroactive legal effect to be exceptionally permissible. The theory and constitutional case law in this area are extensive and must be considered by the legislator when enacting a law with retroactive effect. However, the Constitution does not specifically regulate the retrospectivity of legal effects, which is why constitutional case law has developed it based on the principle of the protection of legitimate expectations, which is rooted in the rule of law. Retrospective effect, as opposed to retroactive effect, is permissible, but the legislator must avoid acting arbitrarily and may worsen the legal position of the addressees only if there is a substantive reason based on an overriding, legitimate and constitutionally permissible public interest, having regard to the principles of proportionality and equality before the law. When amending an existing regulation which worsens the legal position of the addressees, the legislator must weigh legislative interference against the principle of the protection of legitimate expectations.

Keywords: retroactivity, retrospectivity, principle of the protection of legitimate expectations, public interest, acquired rights.