The Constitutional Court asserts in its rulings that Article 8 at a general level determines the relationship between international law and the legal order of the Republic of Slovenia.²⁵ International law and domestic law are therefore considered as two separated systems. This view is also shared by Slovenian legal theory,²⁶ which means that a dualistic approach towards the relationship between international and national law has been adopted. Nevertheless, there are some elements of monism, which can be noticed in the way international treaties are endorsed in the domestic legal order. This endorsement does not require specific legislation, but only confirmation of an act of ratification and the consequent direct application of the provisions of international treaties.

In addition to Article 8, Article 15 of the Slovenian Constitution, which concerns the exercise of human rights and fundamental freedoms, relates to the status of international law in Slovenia. Article 15(5) provides that ‘no human right or fundamental freedom regulated by legal acts in force in Slovenia may be restricted on the grounds that this Constitution does not recognise that right or freedom or recognises it to a lesser extent’. The Constitutional Court ruled that ‘Article 15(5) gives human rights and fundamental freedoms, recognised by ratified international treaties, constitutional rank’.²⁷

Generally accepted principles of international law are not often used as a standard of review in the case law of the Slovenian Constitutional Court.²⁸ It has, however, defined their meaning. The Constitutional Court says that generally accepted principles of international law include general legal principles recognised by civilised nations, as well as rules of international customary law. Therefore, in the case concerning military courts, the Court found:

The provisions of the Decree on Military Courts of 24 May 1944, which even at the time of issuing and application conflicted with the general legal principles recognised by civilised nations as well as the Constitution of the Republic of Slovenia, shall not be applied in the Republic of Slovenia.²⁹

Furthermore, in the case concerning ‘stolen kids’ the Court found that ‘(j)udicial state immunity has developed on the basis of state practice to become international customary law’.³⁰

The Court is competent to review the consistency of legislative and executive acts with generally accepted principles; it cannot, however, present a standard of review of international treaties in the procedures of a priori references of constitutionality.³¹

Many generally accepted principles of international law concern relationships between states (e.g. peaceful resolution of conflicts, principle of equality of states, principle of non-intervention, etc.) and are therefore rarely applied in domestic judicial procedures.³² The exceptional situation concerns ex post review of acts of ratification of international treaties. In this respect, the Constitutional Court in the case concerning the Agreement between the Republic of Slovenia and the Republic of Croatia on Border Traffic and Cooperation interpreted the principle uti possidetis and ruled that it is ‘a generally accepted principle of international law and as such applies also to Slovenia’.³³ When applying these principles it is particularly difficult to decide whether a certain rule or principle actually is a generally accepted principle of international law. In this respect, in its older case law, the Constitutional Court did not allow references to the General Declaration on Human Rights, explaining that it did not have the power and nature of an international treaty, whereas later it started to treat it as part of international customary law.³⁴

In general, the Constitutional Court has applied generally accepted principles of international law mostly in relation to the regulation adopted during World War II and immediately afterwards. In Case U-I-23/93,³⁵ it reasoned from the fact that after WWII the international legal order was established on the basis of the condemnation of the Nazi and Fascist regimes and the persecution of the perpetrators responsible for the crimes committed, which was confirmed by the entire international community of that time. In the mentioned decision, the Constitutional Court took the position that certain activities of an individual during the war can be a reason for such a person not to be entitled to Yugoslav citizenship. In the case concerning the Victims of War Violence Act,³⁶ the Court ruled that:

Legislation which recognizes the status of victim of war violence to persons who collaborated with the occupying forces would be inconsistent with the generally valid principles of international law, and thereby also inconsistent with the Constitution.³⁷

In this respect, it should also be mentioned that in the case concerning the Convention against Torture,³⁸ Judge Škrk stated in her concurring opinion that:

we cannot overlook the fact that the Convention against Torture, which defines torture as an offence under criminal law, was adopted on 10 December 1984. Today, the prohibition of torture, alongside the prohibition of genocide and grave massive breaches of human rights, is among the absolutely binding (peremptory) norms of customary international law (ius cogens), which have erga omnes effects. It is thus the case of norms in international law which in the hierarchy of legal norms are above other norms and principles of international law.³⁹

What constitutes an international treaty is at an informal level left to the Ministry for Foreign Affairs. In line with the Vienna Convention on the Law of Treaties, the Slovenian Foreign Affairs Act defines an international treaty in Article 69.⁴⁰ The second paragraph of the same provision states that an opinion on whether an international instrument is an international treaty shall be given by the Ministry of Foreign Affairs before the commencement of the procedure for the conclusion of an international treaty. This is a soft-law provision, as in the case of dispute the Constitutional Court is competent to define what constitutes an international treaty.⁴¹

The Constitutional Court has adopted a broad interpretation of international treaties, so that Article 8 of the Constitution also encompasses treaties sui generis (e.g. Vatican accords, concordats, pacts, etc.). In its ruling concerning the Agreement between the Republic of Slovenia and the Holy See, the Court had to determine whether the Agreement was an international treaty, as it would otherwise not be competent for its review. The Court found:

The Agreement is being reached by the Republic of Slovenia as an independent and autonomous State and the Holy See as a sui-generis subject of international law. Treaties that the Holy See enters into as the highest and sovereign authority of the universal Catholic Church refer to the issues that are directly connected with the Catholic Church in States – treaty parties (…). Irrespective of the special character of agreements between the States and the Holy See (known as concordats, conventions, covenants, modus vivendi, protocols or agreements) the prevailing theory of international law treats them as real treaties, which do not only confirm the existing rights of treaty parties (e.g. the free activities of the Church), but can also create new rights and obligations for both sides. What applies to the interpretation of these agreements as well as to treaties entered into by States are the rules of the Vienna Convention on Contract Law (…), which was also signed and ratified by the Holy See.⁴²

It should also be emphasised that in the case concerning the Act on the Reestablishment of Agricultural Communities and Restitution of their Property and Rights, the Constitutional Court stated that legislation, which would condition enforcement of a ratified and published international treaty binding upon Slovenia with the adoption of a new international treaty, would contravene Articles 8 and 153(2) of the Constitution.⁴³

Ratification and publication of international treaties are of paramount importance for their application.⁴⁴ In the Case Rm-1/97 concerning the European Association Agreement, the Court held:

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  Article 8 of the Constitution provides that proclaimed and ratified international agreements shall apply directly. From the viewpoint of international law, ratification is unilateral declaration of intention of one contracting party addressed to the other contracting party, to the effect that it accepts the content of a signed agreement as binding. Such declaration of intention is delivered by the State on the occasion of exchanging instruments of ratification. According to the provision of indent 5 of article 107 of the Constitution, such instruments are published by the President of the Republic.
  
  
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  However, the President of the Republic may publish such instrument of ratification after the National Assembly has passed the law on ratification of an international agreement. The instrument of ratification is an international act, and the law on ratification is an act under internal law, whose importance is twofold. On the one hand, it is a sort of authorization granted to the President of the Republic, allowing him to publish an instrument of ratification and, on the other hand, it is a normative act by which obligations under international law are transformed into internal law of the State (…).
  
  
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  Thus, provisions of an international agreement are integrated in the internal legal system of the Republic of Slovenia with the coming into force of such agreement on condition that they have been ratified in accordance with the internal law of the Republic of Slovenia. By an international agreement, rights and obligations are created for the State.
  
  
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  When the international agreement has been approved by the law on ratification, it can create rights and obligations also for natural and legal persons in the country if its provisions are by their nature such that they make this possible (in the case of the so called ‘self-executing treaty’).⁴⁵

This subject-matter has also been explored by the Constitutional Court in the case concerning the Agreement between the Republic of Slovenia and the Republic of Croatia on Border Traffic and Cooperation. In relation to the effects of ratification the Court held⁴⁶:

Ratification⁴⁷ creates internal legal effects of an international treaty; the latter becomes a part of the domestic legal order. This does not change the international obligation of the state. Quite to the contrary, with ratification of an international treaty the state upholds international obligations covered by international law (…) Non-fulfilment of the obligation is a breach of the treaty – it means that the court has made an international tort.

If a treaty is not ratified and published in the Official Gazette, it does not apply in Slovenia.⁴⁸ This was clarified by the Constitutional Court, e.g. in the case concerning the Israeli Agreement, which was signed by army officials only.⁴⁹ However, it is sufficient if the act of ratification is only published in the Slovenian language.⁵⁰

From the point of view of ratification, two groups of treaties must be distinguished:

The former are considered to be hierarchically above laws, whereas the latter are considered to be below laws, adopted by the National Assembly.⁵¹ The internal hierarchy of legal acts per se does not affect the fulfilment of international treaties. Problems could therefore arise if the provisions of such a treaty are inconsistent with a national act of a higher rank (the Constitution, a law), as the constitutional demand for consistency of legal acts requires primacy of the constitution over all international treaties and primacy of parliamentary acts over international treaties ratified by the Government—whereas the principle of international law ‘pacta sunt servanda’ requires respect of international treaties bona fide.⁵² It should also be emphasised that the Government may not ratify a treaty if this requires the adoption of new laws or the changing of existing ones.

The second paragraph of Article 8 of the Slovenian Constitution provides that international treaties apply directly. Direct application, however, is possible only of so-called ‘self-executing’ treaty provisions—i.e. provisions that concern individuals and contain sufficiently clear and precise rights and obligations for the parties to invoke them before the courts.⁵³ Whether a treaty provision is self-executing must be determined on a case-by-case basis by the national courts.⁵⁴ When this is not the case, the treaties oblige the authorities to adopt further regulation.

So, for example, the Constitutional Court decided in a case concerning the Convention on Children’s Rights that the Convention is directly applicable and overrides a provision of Slovenian law on the right of a child to keep contacts with his parents. The Court claimed that the principle ‘lex posterior derogate legi priori’ does not apply in the relation between the Convention and national legislation, but that the former is hierarchically higher than the latter. On the other hand, as regards some procedural rights of children guaranteed by the European Convention on the Exercise of Children’s Rights, the Court decided that they are not directly applicable and cannot be assured without appropriate legislative action of the national authorities:

If treaties are not directly applicable, such ratified and published treaties create international obligations for the state to adopt in its national legal order appropriate national legal acts by which it ensures compliance with such obligations.⁵⁵

In this respect also the Constitutional Court’s ruling on the Convention against Torture is illustrative. The Court found therein that:

Most certainly, the Convention against Torture does compel the legislature to incriminate torture in (the Criminal Code) and such in a form as the aforementioned criminal offence is defined in Article 1 of the same. The Convention against Torture leaves it to the national legislature to determine the penalties for such, while it compels the legislature to define torture as regards the prescribed penalties as a grave criminal offence. Thus, such requirements of the Convention against Torture cannot be ascribed the nature of self-executing provisions or provisions that can be applied directly before Slovenian criminal courts. The impediment to the direct application of the Convention against Torture in the prosecution of alleged offenders of torture is the requirement to respect the principle of legality (nullum crimen nulla poena sine lege praevia), which is a universally recognized general principle of law, recognized by civilized nations and determined in Article 28 of the Constitution. However, the obligations accepted by means of treaties bind the state to comply with such obligations. (…) As regards the discussed issues, the Constitutional Court refers to the generally recognized treaty law principle of pacta sunt servanda, which compels contracting states to perform treaties in good faith.⁵⁶

When an international treaty provision is in conflict with a domestic law provision, the question arises whether a national judge may adopt a ruling that is faithful to international law. If the conflicting national law was adopted prior to the applicability of an international treaty in Slovenia, judges should follow the Constitutional Court position that the hierarchically higher provisions of the treaty override the contrary provisions of national legislation. However, when contrary national legislation was adopted after the international treaty started to apply in the domestic legal order, it is disputable whether a judge may apply the international treaty provision or whether he should start a procedure for a constitutionality review of the conflicting law before the Constitutional Court. The Slovenian Constitutional Court has still not decided on this matter. However, on the basis of its human rights case law, Umek concludes that judges may deliver a ruling themselves if consistent interpretation of domestic law in the light of the treaty is possible. In the opposite situation, however, they should ask the Constitutional Court for a constitutionality review.⁵⁷

The Constitutional Court has developed several approaches to the review of national regulation in the light of international treaties and generally accepted principles of international law.

When interpretation of a right under an international treaty is comparable to the interpretation of a right under the Slovenian Constitution, the Court considers the asserted breach of the right on the basis of the Constitution only. Consequently, the Court ruled that Article 6 of the European Convention on Human Rights (ECHR) does not assure a broader right to effective judicial protection than the Constitution and therefore reviewed the challenge only in light of Article 23 of the Constitution.⁵⁸ Similarly, the Court reviewed the requirement that courts in civil proceedings should enable parties to use a language which they understand only in the light of Article 62 of the Constitution,⁵⁹ whereas the Court only reviewed the asserted procedural mistakes, which also breached Article 6 ECHR, in light of Articles 22 and 23 of the Constitution.⁶⁰ The Court noted that these two provisions ‘guarantee at least such extent of protection as the first paragraph of Article 6 ECHR’.⁶¹ Another example in this series of cases concerned the right to property as assured by Article 1 of the First Protocol to the ECHR, but which is also regulated by Article 33 of the Constitution. For this reason the Court reviewed the asserted breach of this right only in view of the constitutional provision.⁶²

When, on the other hand, the substance of international treaty provisions does not overlap with similar provisions of the Constitution or when the latter does not contain any similar provision, the Court reviews the contested provision of national law directly in the light of the relevant international treaty. In this respect, the Court usually uses the Vienna Convention on the Law of Treaties and legal doctrine as well as the case law of international courts and other institutions.

Consequently, in the case concerning the Lipica Stud Farm Act, the Constitutional Court reviewed the Act in the light of the Aarhus Convention and ruled:

The provision of the Act on the Amendment to the Lipica Stud Farm Act which with regard to the spatial regulation plan excludes a procedure for the preparation and adoption of such a plan in accordance with general spatial regulations although the plan is considered to be a state detailed area plan, and thereby also prevents the public from participating in such, is inconsistent with the Aarhus Convention.⁶³

Particular importance is given to the case law of the European Court of Human Rights (ECtHR), which is binding upon Slovenia. For example, in a case concerning the right to a trial, the Slovenian Constitutional Court emphasised:

Irrespective of its positions mentioned in the previous paragraph of the reasoning, in the review of the challenged Administrative Dispute Act’s provisions the Constitutional Court must consider the case law of the ECtHR, according to which the effective judicial protection of the right to a trial within a reasonable time is ensured only if it also encompasses protection which affords appropriate satisfaction. The Constitutional Court must consider this case law irrespective of the fact that it was adopted in a case in which Slovenia itself did not participate in proceedings before the ECHR. It namely concerns a clear and well established practice of the ECtHR, according to which conditions which must be fulfilled are determined in abstract so that concerning the ECHR it is possible to consider that the legal system of any contracting state contains an effective legal remedy against the violation of the right to a trial within a reasonable time also in cases in which a violation has already ceased.⁶⁴

Furthermore, in a case concerning the Housing Act, the Constitutional Court stated that although the Slovenian Constitution does not recognise the right to a home, this does not mean that such a right is not guaranteed by international treaties that are binding upon Slovenia, and consequently relied on Article 8 ECHR and the ECtHR ruling in Larkos v. Cyper.⁶⁵ It derives from here that the Constitutional Court relies on the case law of the ECtHR in all relevant cases, not only when reviewing the compatibility of a law or decree with the ECHR or when considering a breach of a right guaranteed by the Convention—irrespective of whether the parties rely on the Convention or not.⁶⁶

It is true, however, that the Court often does not expressly use international law as a standard for review of the national law, but it is evident only from its reasoning that the Court also used international law when reviewing a provision. For example, in its ruling concerning the Criminal Procedure Act, the Court found that ‘(t)he regulation determined in the Criminal Procedure Act (…) according to which the President of the court appoints a legal representative without obtaining the prior opinion of the defendant, is not inconsistent with the Constitution.’ However, from its reasoning it follows:

Neither the Constitution nor the ECHR and International Covenant on Civil and Political Rights grant a defendant the right to require the right to choose a legal representative also in cases in which a legal representative is appointed ex officio. (…) It does not follow from the text of the above-mentioned provisions of ECHR or from the case law of ECtHR that a defendant should be guaranteed the right to a particular legal representative in cases in which a legal representative is appointed ex officio.⁶⁷

Furthermore, in the case concerning the Non-litigious Civil Procedure Act, the Constitutional Court reviewed compulsory detention in closed wards of psychiatric hospitals and in this respect in its reasoning relied on the case law of the ECtHR:

The European Court of Human Rights (hereinafter ECtHR), deciding in the case Winterwerp v. The Netherlands, determined three fundamental requirements that must be met for the detention of mental patients to be lawful. According to the ECtHR, involuntary commitment is allowable only if the mental disorder has been reliably demonstrated based on objective medical expertise, and if the patient’s mental disorder is of such a kind or such a gravity as to make him an actual danger to himself or to others. The third demand refers to the duration of commitment. Commitment may last only as long as the mental disorder justifying it persists.⁶⁸

A constitutional complaint is a legal remedy by which a constitutional complainant in proceedings before the Constitutional Court claims a violation of human rights or fundamental freedoms.⁶⁹ A constitutional complaint cannot be lodged due to the erroneous application of substantive or procedural law or due to an erroneously established state of the facts in proceedings before courts. A constitutional complaint may, as a general rule, be lodged against a judicial decision only after all (ordinary and extraordinary) legal remedies in the Republic of Slovenia have been exhausted.⁷⁰ As such, it cannot be used to claim breaches of Article 8 as a fundamental constitutional principle.⁷¹ Nevertheless, the complainants may challenge breaches of rights that have been made by wrongful interpretation or application of international treaties and generally accepted principles of international law under the same conditions as are imposed for a review of wrongful interpretation or application of domestic regulation. Further, the complainants may directly challenge breaches of human rights guaranteed in international treaties that are binding upon Slovenia. In practice, the most frequent document of reference is understandably the ECHR, but also the International Covenant on Civil and Political Rights and the General Declaration on Human Rights that is considered as international customary law in Slovenia and as such directly applicable. With the entering into force of the Lisbon Treaty, the Charter of the EU on Fundamental Rights also gained binding force and as such needs to be applied by the Slovenian Courts.