Symposium on Ljubljana – The Hague Convention on Mutual Legal Assistance: Critical Reflections – Fulfilling the Potential of this Landmark Treaty

Symposium on Ljubljana – The Hague Convention on Mutual Legal Assistance: Critical Reflections – Fulfilling the Potential of this Landmark Treaty

[Frederika Schweighoferova is the Director of Parliamentarians for Global Action’s (PGA) International Law and Human Rights Program]

The author participated in the negotiations of the Ljubljana-The Hague Convention in May 2023 on behalf of PGA.


The long-awaited adoption of the Mutual Legal Assistance Convention (The Ljubljana – The Hague Convention on International Cooperation in the Investigation and Prosecution of Genocide, Crimes against Humanity, War Crimes and other International Crimes) on 26 May 2023 by consensus was greatly welcomed by all 70 present States delegations as well as wider international community. The Convention represents a landmark international treaty that clarifies and lays down States’ obligations regarding legal cooperation and extradition in the investigation of genocide, crimes against humanity, war crimes, as well as other international crimes. After 12 years of negotiations, the adoption seizes a historic opportunity to close the gap in effective cooperation among States for international crimes, significantly reduce impunity for perpetrators of these crimes and help to deliver justice and reparations to victims.

Scope of the Convention 


The scope of the years-long negotiations – also echoed in the last two weeks leading to the adoption- were revolving around recurrent questions- should the Convention address exclusively extradition and mutual legal assistance–as such, be of “pure MLA treaty”, or should it also cover substantive criminal law issues? If the latter, should it copy-paste the Rome Statute three core crimes (or four- also including the crime of aggression, “the supreme international crime” as affirmed by the Nuremberg Tribunal) or leave room for developments by not explicitly laying down the provisions of the crimes? Should the amendments to the Rome Statute adopted since 1998 be included in the main text, or only available as an opt-in expansion only? If the latter, would such an opt-in solution not lead to a fragmentation of international obligations? 

In the end, despite intense negotiations on these and other aspects, including, among others, victims’ rights, data protection, scope of domestic jurisdiction, which incorporates the principle of aut dedere, aut judicare (obligation to extradite or prosecute) for all crimes applicable under the Convention (and, where there is no recourse to extradition, imposes obligation to establish suspect’s presence-conditioned universal jurisdiction), the Conference adopted the Convention with a broad scope, addressing both substantive and procedural issues. It further contains important provisions on role and rights of victims; outlaws the statute of limitations for the crimes; improves language on gender in comparison to the Rome Statute and includes comprehensive provisions on assets recovery. The expanded wording of the provisions on asset recovery (Art. 45-46), incorporated as a result of strong advocacy of NGOs, paves the way towards supporting existing or future international comprehensive compensation mechanisms, such as the recently established Register of Damage Caused by the Aggression of the Russian Federation Against Ukraine by the Council of Europe Summit.

In some other aspects, however, the outcome of the negotiations has leaned towards a more cautious approach. The international crimes included in the main text are the three core Rome Statute crimes defined in its 1998 version (genocide, crimes against humanity and war crimes) plus eight optional annexes (including the crime of aggression, five Rome Statute amendments on war crimes as well as two stand-alone crimes on torture and enforced disappearances, i.e. those outside of the framework of crimes against humanity or war crimes).

Expansion and Opt-in 

For the eight annexes, the application of the Convention is only activated if States opt-in (Art. 2(2)). States can also enter in ad hoc bilateral agreements (Art. 6) in case they would wish to expand the application of the Convention to other crimes if all of these conditions are met

The conduct (i) is a crime of genocide, crime against humanity, war crime, crime of aggression, torture or enforced disappearance under international law as well as (ii) under the domestic law of the requesting State Party and (iii) the conduct is an extraditable offence under the domestic law of the requested State Party.

While the adoption and the option to expand the scope of application of the Convention to other international crimes constitutes a critical achievement, it is regretful that States did not seize this opportunity to incorporate the post-1998 developments of international law into the main text of the Convention and merely included them in the annexes as optional opt-in(s), settling for the – especially by the Rome Statute parties- lowest common denominator. Consequently, any cooperation relating to the post-1998 additions of war crimes, stand-alone crimes of torture and enforced disappearances, and, most importantly, the crime of aggression, will be rather optional and only limited to some, usually the most committed States.

Crime of Aggression

And it is lack of inclusion of the crime of aggression that is quite startling. Since the adoption of the Kampala Amendments on the crime of aggression in 2017 and its entry into force in July 2018, this crime has never sparked so many conversations as since the beginning of the aggressive war launched by the Russian Federation against Ukraine in February 2022. This blatant commission of the crime of aggression, sparking a mobilised international response, led to an abrupt awakening as to how the limited jurisdictional regime by the International Criminal Court (also a result of States negotiations) ties the Court’s hands in bringing the perpetrators of this crime to justice. In response, alternative methods have been sought to ensure accountability of the leaders who would have otherwise enjoyed immunities shielding them from trials by domestic courts. Efforts by States and civil society (including Parliamentarians for Global Action) have been launched to remedy the ICC’s jurisdictional limitation, whilst the creation of the Special Tribunal has increasingly found itself in a political spotlight. One would think (and hope) that such development would prompt States to properly acknowledge how the limitations relating to jurisdictional issues – procedurally or substantively- may eventually backfire, and only lead to resorting to more cumbersome solutions. 


Laying down rules for an effective State-to-State cooperation, the Convention benefits all States, irrespective of their status to the Rome Statute, as the International Criminal Court (ICC) only establishes rules for a vertical, States-ICC cooperation. States will thus be able to participate in a system of horizontal cooperation against impunity whereby they support each other in the effort to close any safe haven. For those States that are not yet Parties to the Rome Statute, the adherence to the Convention can demonstrate their commitment to inter- State cooperation. As such, if widely ratified, the Convention will not only strengthen international legal cooperation, but will also improve the effectiveness of domestic proceedings, in compliance with the principle of complementarity. The complementary principle, which attributes primary competence and authority to investigate and prosecute international crimes to States, is further reinforced through the obligation to criminalise the applicable Convention crimes within States’ domestic legislations (Art. 7). Without effective domestic implementation of these crimes, States would not be equipped to try the crimes domestically or recognise crimes-relating decision in an effective and expedited manner. 

Aut dedere, aut judicare and Permissible Reservations

Of particular relevance for the international law development is the provision on the inclusion of the aut dedere, aut judicare for all the crimes applicable under the Convention (Art. 8(3)), imposing an obligation to “take such measures as may be necessary to establish its jurisdiction […] where the alleged offender is present in any territory under [a State’s] jurisdiction and [the State] does not extradite the alleged offender to any of the States […], or surrender the alleged offender to a competent international criminal court or tribunal.

As such, where there is no recourse to extradition, the article imposes obligation to establish conditional universal jurisdiction based on the presence of the suspect at the State’s territory. The inclusion of this provision is of great importance as it enshrines a treaty obligation to extradite or prosecute perpetrators of genocide, crimes against humanity, war crimes, as well as other international crimes, serving to minimize ‘safe havens’ for those responsible for these gravest crimes and to fulfil the victims’ right to remedy.

Nevertheless, as this obligation was opposed by some States, a new provision (Art. 92(3)) was incorporated into the Convention, enabling formulating “reservations or renewable periods of three years, based on grounds existing in its domestic law and in accordance with its obligations under international law, limiting the establishment of its jurisdiction under article 8, paragraph 3.As stated by Amnesty International, States managed to carve out “an exemption and securing discretion on whether to investigate and prosecute suspected perpetrators present on their territory, when this should be a universal duty.”

For this reason, it is of utmost importance that States proceed to the ratification without formulating such reservation. Under international law, reservations are permissible unless (a) the reservation is prohibited by the treaty; (b) the treaty provides that only specified reservations, which do not include the reservation in question, may be made; or (c) in cases not failing under (a) and (b), the reservation is incompatible with the object and purpose of the treaty (Art. 19, Vienna Convention on Law of Treaties). While the reservation to this provision is permissible under (a) and (b) and even explicitly mentioned in the Convention, it may be subject to question whether formulating such reservation, possibly enabling the alleged offender to escape justice, would not go against the object and purpose of the treaty, which is to “facilitate international cooperation in criminal matters between States Parties with a view to strengthening the fight against impunity for the crime of genocide, crimes against humanity, war crimes, and, where applicable, other international crimes” (Art. 1).

It is therefore of the utmost importance that States adhere to the Convention without submitting reservations on this provision. 

Way Forward

Nevertheless, while the expected lessons learned may have not expanded the inclusivity of the material scope of the Convention, one can hope they would manifest in the inclusivity of the ratifications. Without universal, or at least worldwide adoption, the Convention- irrespective of its quality and great potential- is just a piece of paper. 

The ceremony for the signature of the Convention will take place on 14 – 15 February 2024 in the Hague. Once the ratification period is open, “the Convention shall enter into force on the first day of the month following the expiration of three months after the date of deposit of the third instrument of ratification, acceptance, approval or accession” (Art. 90(1)). Thereafter, for all other States joining, the Convention shall enter into force on the first day of the month following the expiration of three months after the date of deposit by such State (Art. 90(2)).

Now the next, and perhaps even more consequential, step is to ensure the wide-spread signature and ratification of the Convention. 

States have already adhered to similar treaties on mutual cooperation to fight transnational organised crime (UN Convention Against Transnational Organised Crime -UNTOC) and corruption (UN Convention Against Corruption -UNCAC). Hence, since the MLA Convention covers the gravest crimes, there should be no technical or logistical objection to prompt ratification. However, those that will abstain from adherence to the Convention may do so on the basis of similar reasons as those States that have not joined the Rome Statute- to preserve impunity of alleged perpetrators, who happen to be, more often than not, States officials.


There had been a pressing need for a multilateral instrument that facilitates inter-State cooperation on mutual legal assistance and extradition in the prosecution of international crimes. Until the adoption of the Convention, there had been no such international or regional treaty. While perhaps not perfect, this Convention satisfies this need and fills the gap. The adherence to the Convention will demonstrate States’ commitment to inter-State cooperation in strengthening the fight against impunity for the gravest crimes of concern to the international community and to ensure that justice and reparations are delivered to communities of victims and survivors of the gravest crimes worldwide.

The remaining step to turn this achievement into real practice is to ensure worldwide ratification of the Convention. All States should therefore sign and ratify the Convention and, to ensure its most effective application, to ratify the Convention without reservations.

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