Failure to define international crimes

In the absence of a domestic definition of the relevant international crime, it seems straightforward to conclude that no prosecution can be initiated at the national level. The Jones case decided in 2006 provides a good example of this situation. The House of Lords held that, under international law ‘the elements of the crime of aggression have been understood, at least since 1945, with sufficient clarity to permit the lawful trial (and, on conviction, punishment) of those accused of this most serious crime’.^{Footnote 18} However, this crime could not be regarded as a crime under domestic law due to the absence of any national legislation giving domestic effect to the prohibition of aggression:^{Footnote 19} ‘It is nowadays for Parliament and Parliament alone to decide whether conduct not previously regarded as criminal should be made an offence.’²⁰

Arguably, aggression is an international crime of a particular nature: it involves the determination of a state act of aggression, an act that most domestic courts would not regard as being justiciable.^{Footnote 21} According to the International Law Commission, jurisdiction over the crime of aggression ‘shall rest with an international criminal court’;^{Footnote 22} the only state that can try a person for aggression in its national courts is the state whose leaders participated in the act of aggression.^{Footnote 23}

However, the Jones case is not an isolated ruling. The absence of domestic criminal legislation has been regarded as an obstacle to prosecution also with respect to other international crimes. Among various cases, reference can be made to the Nulyarimma case decided by the Federal Court of Australia in 1999. According to Judge Wilcox, while genocide is undoubtedly prohibited under a peremptory norm of customary international law,^{Footnote 24} ‘in the absence of enabling legislation, the offence of genocide is not cognisable in the courts of the Australian Capital Territory’.^{Footnote 25}

In a recent decision, the Special Tribunal for Lebanon has held that, ‘as a general rule, international norms criminalising conduct are non-self-executing, for their implementation requires national legislation defining the crime and the relevant penalty’.^{Footnote 26}

The major obstacle to national prosecution in these cases seems to derive from a strict application of the domestic principle of legality according to which ‘a person may only be held criminally liable and punished if at the moment when he performed a certain act, the act was regarded as a criminal offence by the relevant legal order or, in other words, under the applicable law’.^{Footnote 27}

In 2000, reliance on the principle of legality precluded the prosecution of Habré, former President of Chad, for crimes against humanity before the Dakar Court of Appeals because, at that time, such crimes did not form part of Senegalese criminal law.^{Footnote 28} This conclusion was recently upheld by the Economic Community of West African States (ECOWAS) Court.^{Footnote 29} On similar grounds, the Extraordinary Chambers in the Courts of Cambodia recently excluded the application of a particular mode of liability, known as the third form of Joint Criminal Enterprise (JCE III),^{Footnote 30} which is routinely applied by international tribunals.^{Footnote 31}

However, it must be stressed that domestic courts have made considerable efforts in securing effective prosecution of those responsible for international crimes and in trying to overcome these obstacles arising under national law. In particular, they have been prepared to apply the domestic principle of legality in a manner more consistent with the international prohibition of international crimes and to apply the requirement of domestic enabling legislation in a more flexible way in order to exercise criminal jurisdiction even on the ground of general rules of reference to international criminal law.

An example of the first situation is provided by the Scilingo case decided by the Spanish Audiencia Nacional. Scilingo was a military officer charged with, among other, crimes against humanity committed in Argentina during the military junta’s ‘dirty war’ between 1976 and 1983. Spanish jurisdiction could only be grounded on the 2003 Spanish law which inserted the prohibition of international crimes in the national criminal code. Thus, the Court had to justify the possibility of applying such provisions to crimes committed before their entry into force. In principle, it was admitted that ‘por mucho que se reconozca la validez universal o erga omnes de dichas normas [criminal law], si no están expresamente recogidas en el derecho interno resultan de facto inaplicadas y posiblemente desde un punto de vista técnico inaplicables’.^{Footnote 32} (Translation: ‘however widely recognized the universal validity or erga omnes of said law, if they are not expressly included in domestic law they are not in fact applied and possibly, from a technical point of view, they are not applicable’.) [ILDC 136 (ES 2005)] However, since international crimes are provided under peremptory international norms, the Court held that domestic law could not preclude the application of the new criminal code provisions to crimes committed before its enactment, provided that the conduct amounted to a crime under international law at the time of its commission.^{Footnote 33}

This principle has been affirmed by other domestic courts, and it was upheld by the Special Tribunal for Lebanon (STL) in its decision of 16 February 2011: while ‘international criminalisation alone is not sufficient for domestic legal orders to punish’ conduct amounting to an international crime, nonetheless the principle of legality allows ‘that fresh national legislation (or, where admissible, a binding case) defining a crime that was already contemplated in international law may be applied to offences committed before its enactment without breaching the nullum crimen principle’.^{Footnote 34}

Human rights treaties confirm that prosecutions on the ground of international law are not in conflict with the principle of legality. Article 7 of the European Convention of Human Rights and Article 15 of the International Covenant on Civil and Political Rights prohibit the retrospective application of criminal law for conduct which did not constitute a criminal offence under national or international law at the time when it was committed, specifying that the trial and punishment of persons for conduct which, ‘at the time when it was committed, was criminal according to the general principles’ of international law is not prohibited. In Kononov, the European Court of Human Rights was asked to decide a case in which the applicant was convicted for war crimes committed in 1944 under Article 68(3) of the 1961 Latvian criminal code.^{Footnote 35} The Grand Chamber dismissed the claim of violation of Article 7 ECHR, and held that – despite the absence of enabling domestic legislation at the time when the crime was committed – ‘international laws and customs of war were in 1944 sufficient, of themselves, to find individual criminal responsibility’.^{Footnote 36} Accordingly, international law allows domestic courts to prosecute those responsible for acts amounting to crimes under customary international law at the time when they were committed, even though such acts are not yet criminalized under domestic legislation, without breaching the principle of legality.^{Footnote 37}

While cases in which it was held that prosecution for international crimes could be carried out regardless of the lack of specific enabling legislation are still isolated,^{Footnote 38} more frequently domestic courts have relied on general rules of reference to international criminal law in order to bring to justice those responsible for international crimes. For example, in the absence of specific domestic provisions, Hungarian authorities instituted proceedings for war crimes on the basis of a 1993 law making a general reference to the Geneva Conventions.^{Footnote 39} Similarly, the Swiss Military Criminal Code makes a general reference in Article 109 to violations of ‘international agreements governing the laws of war or the protection of persons and property’ as well as violations of ‘any other recognized law or custom of war’. On the basis of this provision, a number of convictions have been entered for war crimes.^{Footnote 40} Reference can also be made to the Arklöv case decided in 2006 by the Stockholm District Court. In this case the accused was prosecuted for crimes committed against Bosnian Muslim civilians during the Balkan conflict. The District Court accepted that, under customary law, certain grave breaches of the Geneva Conventions were also prohibited in internal armed conflicts, and that the accused could be convicted according to chapter 22, section 6, of the Swedish Penal Code, which criminalizes the violation of ‘generally recognized principle[s] … relating to international humanitarian law concerning armed conflicts’.^{Footnote 41} It must be pointed out that in those cases the prosecution for international crimes was possible because domestic courts could nonetheless rely on national provisions making reference to international criminal law, although drafted in broad terms.

More generally, the approach of domestic courts described above undoubtedly confirms the separation of international law and domestic legal orders. On the other hand, the efforts made by domestic courts to overcome certain obstacles connected to this separation should be appreciated. In general, the courts show a willingness to carry out, as far as possible, effective prosecution for international crimes and to adapt domestic standards to the needs of international criminal law. Thus, when they adapt the domestic principle of legality in order to take into account the criminalization under international law of international crimes, domestic courts recognize the existence of a separate international legal order and its competence to establish individual criminal responsibility over conduct amounting to international crimes.

Still, there are situations in which the lack of enabling legislation is particularly problematic. When international criminal law imposes upon states a duty to exercise jurisdiction over the authors of international crimes, the absence of national criminalization precludes the exercise of domestic jurisdiction.^{Footnote 42} The duty to prosecute is certainly to be distinguished from the duty to criminalize. However, the former is generally imposed on states in conjunction with the latter. Moreover, even if the person could be charged with a corresponding domestic offence, a conviction for an ordinary crime is substantially different from a conviction for an international crime.

Indeed, in the absence of national enabling legislation, domestic courts could prosecute the accused for a domestic offence criminalizing the conduct amounting to an international crime. Just to give an example, under Norwegian law a person accused of genocide could be charged with ‘homicide under especially aggravated circumstances’.^{Footnote 43} However, there is a considerable difference between charging the accused with homicide rather than genocide. As pointed out by the International Criminal Tribunal for Rwanda (ICTR), the ordinary offence of homicide has different legal requirements from the international crime of genocide, and genocide is characterized as a crime of particular gravity.^{Footnote 44} Accordingly, the Trial Chamber concluded that ‘Michel Bagaragaza’s alleged criminal acts cannot be given their full legal qualification under Norwegian criminal law’.^{Footnote 45} This is not to deny that prosecution of international crimes as ordinary offences can be efficient, provided that it reflects the gravity of the crime.^{Footnote 46} However, the qualification as a domestic offence rather than as an international crime can have significant consequences for the application of the principle of universal jurisdiction, immunity rules, statutes of limitation, amnesty laws, rules on interpretation, and so on.

Failure to define international crimes consistently with international law

Today, a large number of States do criminalize international crimes in their domestic legislation. However, it may happen that the domestic definition of an international crime is different from the definition provided under customary international law. This may be the source of considerable uncertainty in the application of the relevant criminal provisions.

A first situation that does not seem particularly problematic is where the domestic definition of a certain international crime is broader than that provided under international law. For example, under Ethiopian law, genocide includes prohibited acts aimed at the destruction of ‘national, ethnical, racial, religious’ (along the lines of Article 2 of the Genocide Convention) as well as ‘political’ groups.^{Footnote 47} The person charged with genocide against a political group is accused of having committed an offence labelled as an international crime, which in reality is an ordinary offence under domestic law. In this regard, the accused in the Mengistu trial claimed that the Ethiopian provision was in conflict with the international law definition of genocide (and was accordingly inapplicable), but the High Court rejected the claim. Indeed, it seems difficult to identify such a conflict. If the criminalization of a certain type of conduct is legitimately provided for under the domestic legal order (in particular with respect to the domestic principle of legality), ‘political’ genocide would undeniably constitute an ordinary crime under Ethiopian law,^{Footnote 48} with all the consequences that flow from its domestic nature.

More uncertainties may ensue when the domestic definition of an international crime is unclear or incomplete. This is quite a recurring situation. Domestic legal orders do not always transpose international crimes in a rigorous manner, and national lawmakers may decide to interpret, rephrase, simplify, or modify the definition of certain international crimes. Even a slight change in the wording of the definition of an international crime can have significant consequences in the establishment of individual criminal responsibility. In these cases the question is whether domestic courts can use international law to complete or make clearer domestic provisions.

In this respect, a particularly interesting trend is emerging in international practice according to which domestic criminal law should be interpreted in harmony with international law. In particular, domestic courts increasingly rely on well-established international case law in order to determine with precision the way in which the prohibition of international crimes should be applied at the national level. Thus, consistent interpretation means opening the domestic legal order to international law, recognizing the competence of international tribunals and adapting national law to increasingly refined international criminal law provisions.

A clear example of this trend is provided by the Mugesera case decided by the Supreme Court of Canada in 2005. The Supreme Court had already had the occasion to point out the importance of interpreting domestic law in harmony with customary international law.^{Footnote 49} In Mugesera, the Court put particular emphasis on the authority of ad hoc tribunals’ case law in the interpretation of domestic criminal law transposing the prohibition of international crimes, and concluded that it was necessary to reconsider its previous case law on crimes against humanity.^{Footnote 50}

Another particularly interesting case is Nyionteze, decided by the Swiss Military Supreme Court in 2001. Although the Appeals Court affirmed that it adopted an interpretation of the nexus with the armed conflict required to establish the commission of war crimes which diverged from that of the ICTR, the Supreme Court felt the need to insist on the absence of any conflict between the two interpretations, and tried to reconcile the approach of the Swiss court with that of the international tribunal.^{Footnote 51}

Other domestic courts opted for a different solution and recognized the direct applicability of international criminal law provisions. One may refer, for example, to the decisions of some military courts in the Democratic Republic of the Congo. Relying on constitutional provisions that provide for the primacy of duly ratified treaties over national law, these courts held that the ambiguity of the domestic legislation criminalizing international crimes justified the direct application of the Rome statute as interpreted by international judicial bodies.^{Footnote 52} The purpose of these decisions was to fill the gaps of domestic legislation and to ensure that international standards are applied uniformly, also including in proceedings before domestic courts exercising jurisdiction over international crimes.

To sum up, the emerging trend in the domestic case law of a number of States is to avoid conflicts as far as possible and to ensure a consistent interpretation and application of national criminal provisions concerning international crimes with the interpretation provided in the case law of international courts and tribunals. This marks a significant development in overcoming the uncertainties connected with domestic enabling legislation inconsistent with substantive rules of international criminal law.

Finally, domestic definitions of international crimes that are narrower than the corresponding international criminal law rules (generally because they provide for additional legal requirements) may be particularly problematic. For example, notwithstanding the recent modifications,^{Footnote 53} the French criminal code still provides for definitions of genocide and crimes against humanity which are in part divergent from international criminal law: in particular, in both cases a ‘plan concerté’ is inserted as an additional requirement to be met. In this case one may wonder whether the conduct amounting to an international crime but not covered by the domestic legislation can nonetheless be the object of domestic prosecution.

The STL in the decision already mentioned affirmed a very broad duty of consistent interpretation that should also be applied to domestic provisions that include narrower definitions of international crimes when compared to customary international law. According to ‘a general principle of interpretation common to most States of the world … one should construe the national legislation of a State in such a manner as to align it as much as possible to international legal standards binding upon the State’.^{Footnote 54} However, it is unclear whether this principle also covers situations in which domestic law could be said to be in conflict with international criminal law. The Tribunal applied this principle and construed the Lebanese provision criminalizing terrorism so as to make it consistent with international law. In the end, Article 314 of the Lebanese criminal code could no longer be considered as being in conflict with international law, notwithstanding the Tribunal’s acknowledgement that the well-settled case law of the Lebanese courts had adopted a conflicting view on the material element of the crime of terrorism.^{Footnote 55} It is difficult to apply the same principle when the domestic provision is clearly at variance with international criminal law.^{Footnote 56}

Exercising jurisdiction over international crimes

Where there are various courts competent to exercise jurisdiction over a certain case the classical concern is that of conflicting decisions. With respect to the prosecution of international crimes, this issue has led to the elaboration of certain mechanisms for coordinating the exercise of criminal jurisdiction by different domestic courts or between international and domestic courts. However, we must not lose sight of the fact that the major concern in this particular field of international law remains the difficulty of bringing to justice those responsible for international crimes and of finding courts willing to prosecute the authors of international crimes.

The Habré case provides a good example of all the difficulties of bringing to trial in particular those most responsible for international crimes even when there is a plurality of potentially competent jurisdictions. The former President of Chad was indicted before a Senegalese court, but the domestic principle of legality precluded the exercise of criminal jurisdiction in Senegal.^{Footnote 57} Thus, criminal complaints were filed in Belgian courts, which tried to exercise jurisdiction on the ground of the passive personality principle. While Chadian authorities had lifted any immunity to which Habré might be entitled, the competent Belgian judge issued an international arrest warrant and requested Senegal to extradite Habré. The Dakar Court of Appeals refused extradition on various grounds and Senegal referred the matter to the African Union, which adopted a decision in 2006 concluding that Senegal should ‘prosecute and ensure that Hissène Habré is tried, on behalf of Africa, by a competent Senegalese court with guarantees for fair trial’.^{Footnote 58} Senegal has not yet taken any step to bring Habré to justice. In 2009, Belgium instituted proceedings before the International Court of Justice against Senegal. In November 2010 the ECOWAS Court held that prosecuting Habré before Senegalese courts would run counter to the principle of legality and that

From a different perspective, this case shows the fundamental role that domestic courts can and should play in securing effective prosecution of international crimes, in particular when there is no competent international criminal tribunal.

In order to achieve the basic goal of international criminal law, domestic jurisdiction over international crimes should be established alongside international jurisdiction. Since Nuremberg, a considerable number of domestic legal orders have expanded their jurisdiction. Today, the prosecution of international crimes before domestic courts is possible on the ground of traditional principles of jurisdiction such as the territoriality principle, the active personality principle, the passive personality principle,^{Footnote 59} and the universality principle.^{Footnote 60} In this perspective, the creation of international criminal tribunals has played a fundamental role. It has stimulated domestic legal orders to enact the necessary legislation^{Footnote 61} and exercise jurisdiction when prosecution before international tribunals can be avoided.^{Footnote 62}

Once the prosecution of international crimes is rendered possible before a plurality of international and domestic courts, certain coordination may be desirable. In this regard, recent international practice shows interesting developments in attempting to coordinate the exercise of criminal jurisdiction both at the vertical level – between international and domestic courts – and at the horizontal level – between different domestic courts.

As regards the coordination of international and domestic courts, precise legal obligations can be found in the statutes of international courts and tribunals. The well-known principles of primacy and complementarity govern the relationship between ad hoc tribunals and domestic courts,^{Footnote 63} and the relationship between the International Criminal Court and domestic courts respectively.^{Footnote 64} Notwithstanding certain differences, both principles pursue a twofold purpose. On the one hand, they aim to ensure that the prosecution is carried out at the international level when domestic courts prove unwilling or unable to proceed. On the other hand, they imply that prosecution should be carried out at the national level every time a domestic jurisdiction has the appropriate means to exercise jurisdiction over international crimes. In this sense, they constitute a strong incentive to carry out prosecution before domestic courts and indirectly to adopt the necessary enabling legislation. In particular, as the mission of the ad hoc tribunals is coming to an end, and with the establishment of the ICC, international prosecution is increasingly assuming a subsidiary role with respect to domestic courts. As in the field of human rights,^{Footnote 65} putting the emphasis on the subsidiary character of the prosecution of international crimes by international courts is meant to ensure compliance with international criminal law by domestic legal orders and to stress their primary role in the fight against impunity.

From a more general perspective, what must be pointed out is the joint task that international and domestic courts have always carried out in bringing to justice those responsible for international crimes. According to what has been called the ‘Nuremberg scheme’,^{Footnote 66} international prosecution should in principle focus on those chiefly responsible for international crimes, while minor players should be left to domestic courts. This scheme was applied after WWII and a special tool – the crime of membership – was designed in order to coordinate the work of the IMT and domestic courts.^{Footnote 67} The same ‘division of labour’ has inspired the completion strategies of the ICTY^{Footnote 68} and ICTR.^{Footnote 69} It has also been adopted to coordinate the work of the ICC with that of domestic courts.^{Footnote 70} In other words, the relationship between international and domestic courts has always been characterized by the common endeavour to ensure an effective prosecution of international crimes.^{Footnote 71}

Thus, complementarity in a technical sense is used to indicate the procedural mechanism according to which the prosecution of international crimes is carried out either at the international or at the municipal level. Rule 11 bis in the Rules of Evidence and Procedure of the ad hoc tribunals and Article 17 in the ICC Statute govern this ‘division of labour’ and provide the criteria to accord priority to either international or domestic jurisdictions.

From a different perspective, complementarity can be seen as a tool stimulating the carrying out of investigations or prosecutions at the national level. The notion of ‘positive complementarity’ or ‘proactive complementarity’⁷² has been widely explored by international legal scholarship. The fact that an international tribunal has the power to step in constitutes a significant incentive to the prosecution at the municipal level of those responsible for international crimes. For example, the case law of the ad hoc tribunals applying Rule 11 bis shows that Balkan States and Rwanda have made clear legislative improvements and are now able to prosecute crimes potentially falling under the jurisdiction of the ICTY and ICTR.^{Footnote 73} The case law of the ICC has raised more criticism since the Court has declared the admissibility of cases on the basis of a broad notion of ‘inaction’ by domestic courts without adopting an active role in promoting national prosecutions.^{Footnote 74} However, some positive developments can be appreciated both at the municipal level^{Footnote 75} and at the regional level.^{Footnote 76}

From the standpoint of the present analysis, the most interesting aspect of complementarity is the particular mechanism of interaction that it establishes between international and domestic law. First of all, complementarity implies the recognition of the existence of other, different legal orders having the power to exercise jurisdiction over international crimes. This assumption – that there is a plurality of competent legal orders – is essential in order to accept the competence of a different legal order and even accord it a priority in prosecution. Second, complementarity includes the control, at the international level, that municipal law is genuinely capable of prosecuting international crimes. In this sense it represents a protection for the accused, since the standards applied by the domestic courts are equivalent to international standards that would have been applied by international courts. Third, the basic condition for the application of the complementarity principle is precisely the correspondence of (substantive and procedural) standards at the international and municipal level (which are not necessarily identical) as they reflect the common purpose of the various legal orders of putting an end to impunity. Therefore, complementarity rests on the separation of legal orders but at the same time constitutes a mechanism to ensure the continuity between legal orders.

The effort to ensure horizontal coordination between the various domestic jurisdictions that might be concurrently competent to prosecute international crimes is one of the most interesting developments of recent international practice. As already mentioned, under customary international law there are no precise obligations in this respect.^{Footnote 77} For example, the application of the res judicata or litis pendens principles to regulation of competition between separate and independent legal orders is highly controversial.^{Footnote 78} While it is difficult to say that there are clear rules governing the matter, practice shows a growing reliance on some general criteria according to which the exercise of jurisdiction over international crimes by different legal orders can be coordinated.

According to the Resolution on ‘Universal criminal jurisdiction with regard to the crime of genocide, crimes against humanity and war crimes’ adopted by the Institut de droit international:

1. c) Any State having custody over an alleged offender should, before commencing a trial on the basis of universal jurisdiction, ask the State where the crime was committed or the State of nationality of the person concerned whether it is prepared to prosecute that person, unless these States are manifestly unwilling or unable to do so. It shall also take into account the jurisdiction of international criminal courts.

2. d) Any State having custody over an alleged offender, to the extent that it relies solely on universal jurisdiction, should carefully consider and, as appropriate, grant any extradition request addressed to it by a State having a significant link, such as primarily territoriality or nationality, with the crime, the offender, or the victim, provided such State is clearly able and willing to prosecute the alleged offender.^{Footnote 79}

Certain jurisdictions accord a similar priority to the state having a close connection with the relevant international crime. For instance, in the Guatemala Generals case the Spanish Constitutional Court held that universal jurisdiction should be excluded where the territorial jurisdiction effectively prosecutes the crime, and that Spanish jurisdiction should be subsidiary to that of the territorial State.^{Footnote 80} Under the German International Crimes Code this priority takes the particular form of an alternation between mandatory and discretionary prosecution. The Federal Prosecutor has the duty to initiate proceedings when there is a specific link to Germany, whereas prosecutorial discretion (including the power to refrain from initiating criminal proceedings) applies to cases in which there is no domestic link to the crime or where another state is exercising jurisdiction over the crime. Thus, the German legal order ensures both a vertical and a horizontal complementarity in the prosecution of international crimes.^{Footnote 81} Finally, the Report of the AU-EU Expert Group on the Principle of Universal Jurisdiction recommends an analogous subsidiarity of the principle of universal jurisdiction and invites States to accord priority to territoriality as a basis for jurisdiction over international crimes.^{Footnote 82}

On the one hand, practice shows increasing attempts to identify those jurisdictions that have a particularly close connection with a certain international crime and therefore deserve priority in the exercise of criminal jurisdiction.^{Footnote 83} On the other hand, the priority accorded to a state with a closer link to the international offence does not exclude the exercise of jurisdiction by other States. States more remotely connected with international crimes do have the power under customary law to prosecute the suspects, but this possibility seems increasingly regarded as a default mechanism.^{Footnote 84} In other words, a sort of complementarity gradually appears as a guiding principle also in the horizontal coordination of concurrent domestic jurisdictions competent to prosecute international crimes. The emergence of criteria allowing the coordination of the prosecution for international crimes before different domestic courts would reduce the interstate tensions that can accompany the exercise of pure universal jurisdiction.^{Footnote 85} More generally, this trend shows a growing acceptance of the proposition that there is no exclusive jurisdiction over international crimes, that there are other ‘external’ legal orders competent to try the perpetrators, and that prosecution of international crimes is a matter of common concern for the entire international community.

Immunities as a bar to prosecution

Among a variety of procedural obstacles to prosecution for international crimes, immunities are particularly interesting because they can constitute a lawful bar to jurisdiction under international law and domestic courts are required to act accordingly. From this perspective, legal pluralism seems to entail a diminished level of protection when international crimes are committed by certain categories of state agents, and at the end of the day what remains is a loophole in the law. However, international and domestic case law show a consistent trend in excluding the possibility for the accused of relying on functional immunity while limiting the applicability of personal immunity.

According to the rule on functional immunity or immunity ratione materiae, domestic courts are prevented from pronouncing on the acts of foreign state organs performed in the exercise of official functions since state conduct is the exclusive province of international law. However, today it is no longer disputed that functional immunity cannot shield state agents from prosecution when they are charged with international crimes either before international or domestic courts.^{Footnote 86} This principle has been constantly affirmed in domestic case law^{Footnote 87} and has been recently restated in the Resolution on ‘the Immunity from Jurisdiction of the State and of Persons Who Act on Behalf of the State in Case of International Crimes’, adopted by the Institut de droit international in 2009.^{Footnote 88}

On the other hand, personal immunity or immunity ratione personae can be a significant obstacle in the prosecution of certain state organs before foreign domestic courts. Personal immunity is a procedural bar to jurisdiction, a special protection accorded under international law to a limited number of state agents who represent the state in order to secure the peaceful development of international relations among states (such as heads of state, prime ministers, ministers for foreign affairs, diplomatic agents, and, to a limited extent, consular agents). While it constitutes a complete shield from prosecution, as it covers both acts performed in the exercise of official functions and acts performed in a private capacity, personal immunity is limited in time to the duration of the mandate of the state organ.

Since personal immunity cannot be invoked at the international level,^{Footnote 89} its application may be problematic in particular when there are no competent international courts because prosecution of the suspect is barred before domestic courts (with the sole exception of the courts of the state of nationality). It is true that, technically speaking, personal immunity is a procedural rule and individual criminal responsibility for international crimes is a substantive rule.^{Footnote 90} Thus, no direct conflict can be envisaged between these rules. As the ICJ held in the Arrest Warrant case, these are ‘quite separate concepts’ and personal immunity ‘can bar prosecution for a certain period or for certain offences; it cannot exonerate the person to whom it applies from all criminal responsibility’.^{Footnote 91} However, in practice it cannot be excluded that, under exceptional circumstances, personal immunity could turn out to be a complete shield from prosecution and consequently would indirectly be in contrast with the rule on individual criminal responsibility. Such extreme situations do not create proper normative conflicts; rather, they entail an ‘occasional collision’⁹² in which the application of the immunity rule frustrates the basic goal of international criminal law and the domestic right of the victims to reparation. A domestic court confronted with the solution of a similar ‘collision’ will not apply a strict primacy of one rule over the other but will arguably have the difficult task to strike a balance between the different interests at stake, that is, the protection of the state and the fight against impunity.^{Footnote 93} Thus, while in most cases the international regime of state agents’ immunities can be reconciled quite easily with the prosecution of international crimes, under exceptional circumstances a particular logic of coordination – a logic distinct from the classical logic of conflict – could be called into question.