A New Tool in the Fight Against Impunity for Core International Crimes
Globalisation has made various aspects of our society more efficient over the past century. At the same time, it also brings with it a certain complexity. This is noticeable, for example, in the prosecution of international crimes. In May 2019, on the occasion of the European Union (EU) Day Against Impunity for Genocide, Crimes Against Humanity and War Crimes, the EU Agency for Criminal Justice Cooperation (Eurojust) affirmed that in three years, genocide and war crimes cases in the EU had risen by about one third. 1,430 new investigations were launched in 2018 alone, amounting to a total of 2,943 pending or ongoing cases regarding core international crimes committed worldwide.
In the 2024 edition of the Universal Jurisdiction Annual Review, a group of non-governmental organizations led by Trial International cited thirteen domestic jurisdictions with pending cases under extraterritorial or universal jurisdiction (60 war crimes charges, 50 crimes against humanity charges, and 22 genocide charges), committed in 35 countries. With respect to Syria alone, the report “includes 49 cases underway in nine prosecuting countries for international crimes committed in Syria and bordering Iraq since 2011” (p. 14).
Finally, the Independent International Commission of Inquiry on Ukraine identified multiple war crimes and crimes against humanity involving torture, consistently committed by Russian authorities. These took place in the areas of Ukraine that fell under Russian control, as well as in investigated penitentiary facilities since the beginning of the war on 24 February 2022.
Due to their extraterritorial character, all these cases present unique challenges. Take the example of a war crime allegedly committed in the territory of State A. The suspect may be a State B national, who escaped to and was apprehended in State C, where prosecution is now launched. Victims and witnesses may in the meantime have fled to State D, while crucial evidence could be located in yet another State. These and other, similar scenarios are not uncommon in the investigation of international crimes and require States to cooperate. To address such a scenario, certain States launched an initiative to establish the Ljubljana-The Hague Convention (LHC). This treaty aims to enable States to effectively address the challenges of international criminal cooperation.
Historical Background
The development of rules in international law relating to the prosecution of core international crimes and to support international cooperation to combat impunity for such crimes is not a novel concept. For instance, the 1949 Geneva Conventions (GC) include rules requiring States party to establish mechanisms in domestic law to actively seek out alleged perpetrators of grave breaches and punish them in national courts or extradite them to another State (GC I, art. 49, GC II, art. 50, GC III, art. 129, GC IV, art. 146).
For States parties to the 1977 First Additional Protocol, an obligation to repress grave breaches and suppress other breaches resulting from a failure to act when under a duty to do so complements these provisions (art. 86). Most importantly, the Protocol contains explicit obligations relating to mutual legal assistance (MLA) in criminal matters (art. 88). However, neither the Geneva Conventions nor the Additional Protocols extended these mechanisms to cover non-international armed conflicts, nor did they impose a fortiori an obligation to introduce these crimes into domestic law.
The existence of war crimes in non-international armed conflicts was later confirmed mainly through international criminal law, culminating with the adoption of the 1998 Rome Statute of the International Criminal Court (ICC). This treaty also sets forth concrete obligations of cooperation (arts. 86 et seq.).
However, the Rome Statute does not contain any provisions relating to “horizontal cooperation” between States for the prosecution and punishment of the relevant crimes within their domestic jurisdictions. The Statute also lacks an explicit obligation to introduce these crimes in States’ domestic legal systems or to establish domestic jurisdiction over these crimes. Reference to this obligation is only made in the preamble of the Statute, which recalls that “it is the duty of every State to exercise its criminal jurisdiction over those responsible for international crimes.”
Moreover, as highlighted by participants in the preparatory conferences leading up to the negotiations of the LHC, what was equally lacking was a conventional framework of up-to-date regulation on practical aspects of international cooperation into criminal matters. This relates particularly to mutual legal assistance, and the extradition or transfer of sentenced persons.
These are the main gaps the LHC seeks to address. At the origin of the Convention lies the so-called Mutual Legal Assistance Initiative launched in 2013 by Argentina, Belgium, Mongolia, the Netherlands, Senegal and Slovenia (the core group). After two preparatory conferences held in person, in 2017 and 2019, the negotiations were scheduled to take place in Ljulbljana in June 2020 but were postponed due to Covid-19. Finally, Ljubljana hosted the diplomatic conference from 15 to 26 May 2023, ending in the adoption of the Convention. The Hague hosted the signing conference from 14 to 15 February 2024 and the Convention became open for signature by all States until 15 February 2025. At the time of writing (end of January 2025), 37 States have signed the Convention.
Material Scope of the Convention
The LHC smooths the path for mutual legal assistance between States. It establishes procedures that enable national agencies to cooperate with other States during the prosecution of alleged perpetrators of certain serious international crimes, including war crimes. The LHC provides a legal framework for these agencies, in cooperation, to efficiently collect evidence, exchange information, extradite persons, and take other actions necessary to combat impunity for such crimes.
The material scope of the Convention is articulated in three levels. On the primary, minimal level, the Convention covers genocide, crimes against humanity, and war crimes (art. 2(1)). Article 5 defines these crimes, reproducing to the letter Articles 6, 7, and 8 of the Rome Statute but with two exceptions: the war crime listed in Article 8(2)(b)(xx) (i.e., employing weapons which are of a nature to cause superfluous injury or unnecessary suffering); and the definition of gender in Article 7(3) of the Rome Statute. These were deleted from the LHC definitions.
On a second level, the Convention contains a list of annexes with additional crimes. Annexes A to E cover all war crimes that were added to the Rome Statute by amendments adopted prior to the 2023 Ljubljana Conference. Annex F concerns torture as it is defined in the 1984 UN Convention Against Torture. Annex G refers to enforced disappearance, as defined in the 2006 UN Convention on Enforced Disapperarance. Lastly, Annex H relates to the crime of aggression, reproducing the definition found in the Kampala Amendment to the Rome Statute of the ICC. States may choose to extend the LHC’s application to one or more of these annexes by a written declaration made at the time of signature of the Convention or at any later time (art. 2(2)).
Finally, Article 6 of the LHC allows States party to apply the Convention ad hoc, to conduct that constitutes genocide, a crime against humanity, war crime, crime of aggression, torture or enforced disappearance even when the domestic law of the requested State qualifies it simply as an extraditable offence, provided that both States (the requesting and the requested) agree to this ad hoc application (see also here).
Jurisdiction
The provisions relating to the establishment of jurisdiction are among the most important of the Convention. As the International Court of Justice held in the case concerning Questions Relating to the Obligation to Prosecute or Extradite (Belgium v. Senegal), the obligation to criminalize the relevant conduct, give domestic courts the required universal jurisdiction, make an inquiry into the facts, and to prosecute or, if possible, extradite the suspect, are inextricably linked. They “may be regarded as elements of a single conventional mechanism aimed at preventing suspects from escaping the consequences of their criminal responsibility” (para. 91).
This logic animates the relevant provisions of the LHC. Article 7 places an obligation on States parties to introduce the crimes with appropriate penalties in their domestic laws. Articles 8 and 14 relate to the exercise of jurisdiction.
Article 8(1) of the Convention provides that each State party must take necessary measures to establish its jurisdiction over international crimes committed in its territory or by its nationals. Article 8(2), meanwhile, provides that States are allowed, but not compelled, to establish jurisdiction over these crimes, should the alleged offender be a stateless person resident in that State’s territory or the victim a national of that State. Finally, the third paragraph of Article 8 establishes universal jurisdiction in cases where the alleged offender is present in a State party’s territory, unless the State in question chooses to extradite the alleged offender to another State or surrender the individual to a competent international criminal court or tribunal.
Following the principle of aut dedere aut judicare as confirmed in the Belgium v. Senegal judgment (see para. 95), States must prosecute individuals under their jurisdiction who are suspected of having committed serious international crimes. Article 14 of the LHC confirms this principle and states that, if the Convention applies and if the alleged offender falls within the jurisdiction of a particular State, that State must submit the case to its competent authorities. Alternatively, it may extradite or surrender the person to another State or a competent international criminal court or tribunal.
Nature of the Convention: Rejecting the “Pure-MLA” Model
The bulk of the Convention contains technical and procedural provisions that cover the various possible forms of cooperation in the prosecution of alleged perpetrators of crimes determined by Article 2. These relate to mutual legal assistance, extradition, and transfer of sentenced persons. The provisions cover, among other things, interrogations through electronic means (art. 34), cross-border observations (art. 42), and confiscation of assets (art. 45). In addition, the Convention also deals with victims’ rights in Articles 81 to 83.
Negotiators were torn between a treaty which that only contain such “technical” provisions on mutual legal assistance, extradition, and transfer of sentenced persons (the so-called “pure-MLA” version) and a treaty that would also include general international criminal law provisions like the obligation to introduce the crimes in domestic law or the aut dedere aut judicare obligation. This decision loomed over the discussions leading up to negotiations and remained open until Ljubljana. In the end, States opted for the latter version, thus creating an ambitious treaty which reinforces and complements other existing instruments and obligations in international law.
Critical views of this choice have argued that a “pure-MLA” treaty may “have done a better job of ‘future proofing’ the MLA treaty” with respect to developments in the definitions of crimes (such as new amendments to the Rome Statute or a potential different definition of crimes against humanity). This criticism appears unwarranted, given that the system of annexes to the Convention is designed precisely so that new crimes can be added to its scope and given the fact that the LHC clearly emphasizes in Article 3 that developing rules of international law, including the definitions of the crimes to which this Convention applies, will not be limited by this Convention.
Beyond that, Article 4 of the LHC provides that States parties may apply another agreement concluded between themselves instead of the Convention, if this facilitates their cooperation. This would, for instance, settle any potential conflict between the LHC and a future crimes against humanity convention, should the latter adopt a definition of crimes which is different from that included in Article 5, paragraphs 2 and 3, of the LHC.
Another criticism against the extended scope of the LHC relates to the appeal of the treaty, arguing that a “pure-MLA” version would be more attractive to States and thus more widely ratified. This argument was considered by States and rejected in Ljubljana, where the negotiating States clearly opted for the ambitious version of the LHC. The underlying belief is that States that are serious about contributing to the fight against impunity will not be discouraged by the obligations set down in its first part. Time will tell whether this choice will prove to have been overly optimistic.
Relations with the International Criminal Court
There are obvious parallels between the LHC and the Rome Statute of the ICC. First, as mentioned above, the crimes to which the Convention applies are copy-pasted from the Statute. Second, the system of annexes reflects to a large extent the system of amendments to the Rome Statute.
Despite these links, the LHC is independent from the Rome Statute and can be ratified without difficulty by States which, for whatever reason, do not wish to accept the jurisdiction of the ICC. This reflects the clear will of the negotiating States expressed since the initial discussions that led to the adoption of the LHC.
At the time of writing, this has worked to a certain—admittedly limited—extent, as illustrated by the fact that some non-member States to the ICC were among the supporters of the LHC (namely Belarus, Kazakhstan, Rwanda, Sao Tomé and Principe, Serbia, and Togo; see list of supporting States of MLA initiative). Rwanda not only participated actively in the negotiations in Ljubljana (see list of participants in the Ljubljana Conference), it is also among its first signatories (see list of signatories of the LHC, updated on 25 June 2024).
Here as well, we will have to wait for the entry into force of the treaty and the future ratifications in order to evaluate whether the Convention will appeal to States which do not belong to the ICC system.
Gap-Filling Function
The Convention fills a major gap in international treaty law. Most importantly, it obliges States party to introduce the crimes to which the Convention applies into national law and establish jurisdiction over these crimes. It also compels States party to prosecute persons accused of commiting these crimes or, if the option is available, to extradite them to a State willing to do so (aut dedere aut judicare). Moreover, the LHC affirms the inapplicability of statutes of limitations for the crimes covered by the Convention (see art. 11). For States party to the Rome Statute, the Convention becomes a tool to ensure the efficient activation of the principle of complementarity (see Rome Statute, preamble and art. 17).
Outside the ICC system, equivalent treaty provisions to those set out in the Convention only exist in respect of some crimes, and to a certain extent. With respect to war crimes, the few relevant provisions in the 1949 Geneva Conventions and the 1977 First Additional Protocol are mentioned above. As for customary law, taking as a point of reference the 2005 International Committee of the Red Cross Study on Customary International Humanitarian Law, the relevant rules are limited to the following:
States have the right to vest universal jurisdiction in their national courts over war crimes (rule 157);
States must investigate war crimes allegedly committed by their nationals or armed forces, or on their territory, and, if appropriate, prosecute the suspects. They must also investigate other war crimes over which they have jurisdiction and, if appropriate, prosecute the suspects (rule 158);
Statutes of limitations may not apply to war crimes (rule 160).
Whether and to what extent each provision in the first part of the LHC codifies existing customary international law or establishes a new obligation is beyond the scope of this post.
The added value of the Convention is that it provides national authorities involved in the prosecution of war crimes (either on the side of the State requesting legal assistance or extradition or on the side of the one receiving the request) with the required legal certainty in terms of the applicable regime and with clear and effective tools for cooperation in prosecution, avoiding the need to navigate the much murkier waters of customary international law. In this sense, the Convention represents a decisive step in combating impunity for core international crimes, including war crimes.
Concluding remarks
The Convention has been qualified as a “landmark international treaty” (see Eurojust, 2023 Annual Report, p. 31). Indeed, it offers a modern framework for legal cooperation on mutual legal assistance, extradition and transfer of sentenced persons in relation to the commission of core international crimes. This framework can be a valuable tool for States that have repeatedly and in various contexts declared the need to effectively combat impunity for core international crimes, including war crimes. The time has come for States to match words with deeds and become parties to the Convention.
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Jan De Gols is a legal advisor for Belgian Defence, specializing in operational law. This article reflects his personal opinion and does not represent the official position of Belgian Defence.
Vaios Koutroulis is a Professor of Public International Law at the Faculty of Law and Criminology of the Université Libre de Bruxelles and a member of the International Humanitarian Fact-Finding Commission. The views in this post are expressed in the author’s personal capacity.
Photo credit: National Police of Ukraine
