To Custom or Not to Custom: A Battle for the Applicable Sources of Law at the Kosovo Specialist Chambers

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Over the past 5 months, the Prosecutor of the Kosovo Specialist Chambers (‘KSC’) and defence counsels for multiple accused have been filing submissions on a legal question that is of utmost importance for the work of the Court: to what extent can the KSC apply customary international law (‘CIL’)? A series of jurisdictional motions, the most comprehensive one of which was filed by the Defence of Kadri Veseli in the Hashim Thaçi et al case, requested the pre-trial judge to find that the KSC lacks jurisdiction over arbitrary detention as a war crime in non-international armed conflicts, as well as over joint criminal enterprise (‘JCE’) and command responsibility. Aside from rejecting the customary legal basis of these constructs, the accused have principally argued that directly applying CIL in Kosovo’s legal order is unconstitutional, unless a domestic statutory provision that incorporated the respective CIL concept in Kosovo at the material time can be found. The KSC is reminded that, as a national court which is part of Kosovo’s judiciary, it is required to comply with alleged constitutional restrictions on the application of customary international law in criminal cases.

A Decision on these submissions was issued by the Pre-Trial Judge Nicolas Guillou on 22 July 2021. It is a remarkable piece of jurisprudence for several reasons, one of which is that it presents the KSC’s first judicial review and affirmation of the controversial customary status of the ‘extended’ JCE category (paras. 180-190). Even more fundamentally for the work of this Court, however, Judge Guillou also confirmed the KSC’s authority to directly apply CIL in its proceedings, albeit in a manner which, in the present author’s opinion, did not fully address the essence of the constitutional challenge raised in Veseli’s jurisdictional motion. In this sense, it seems highly unlikely that this decision would put the matter to rest.

This contribution examines the arguments that Veseli’s Defence has raised to challenge the application of CIL at the Kosovo Specialist Chambers and then provides critical reflections on Judge Guillou’s respective findings on this matter.

Defining the Applicable Law at the KSC: The Approach Adopted in the Law on Specialist Chambers and Specialist Prosecutor’s Office (‘KSC Law’)

The applicable law at the KSC is defined in Article 12 KSC Law, which establishes customary international law as one of the Court’s two sources of law, the other one being “the substantive criminal law of Kosovo insofar as it is in compliance with customary international law”. Article 3(2)(d) KSC Law further underscores the role of CIL as a primary source of law at the KSC by directing the Court to adjudicate its cases in accordance with “customary international law, as given superiority over domestic laws by Article 19(2) of the Constitution”. The said two articles could hardly be clearer on how the legislator – i.e., the Assembly of the Republic of Kosovo – envisioned the applicable law at the KSC. Customary international law, as it existed during the Court’s temporal jurisdiction (1 January 1998 – 31 December 2000), is the law that KSC judges are called to apply, while Kosovo’s domestic criminal law is designated as a secondary source of law, applicable to the extent that it does not conflict with CIL.

Much less clear, however, is how this arrangement fits in Kosovo’s national legal order: an important consideration, given that the KSC is not a supranational court which exists outside the judicial system of Kosovo. The legal basis of the KSC is a domestic legislative act (i.e., not and international agreement, or a UN resolution), which unequivocally states that the Specialist Chambers function “within the Kosovo justice system” (Article 1(2) KSC Law) and are thereby “attached to each level of the court system in Kosovo: the Basic Court of Pristina, the Court of Appeals, the Supreme Court and the Constitutional Court.” (Article 3(1) KSC Law) To be sure, one can still argue that there are some elements – such as the international staffing of the KSC, or the international efforts underlying the establishment and funding of the Court, its seating in the Netherlands, etc. – which “internationalize” the KSC. However, this does not detract from the fact that the KSC is decidedly part of Kosovo’s judiciary, operating within Kosovo’s legal order (Williams, pp. 27-20). The KSC Law thus cannot be read as a self-contained legal regime, which is insulated from and unfettered by Kosovo’s other municipal laws and, specifically, by the supreme law of the land: the Constitution of Kosovo. On the contrary, Article 3(2)(a) KSC Law states that the Court must exercise its functions in compliance with the Constitution: i.e., the KSC Law is very much subject to the constitutional safeguards applicable in Kosovo.

Accordingly, counsels for the accused Rexhep Salimi, Pjetër Shala, Hashim Thaçi, and Kadri Veseli filed a series of jurisdictional motions that raise a poignant question: does Article 12 KSC Law, via which the Assembly of the Republic of Kosovo mandated the KSC to directly apply CIL, comply with the constitutionally established regime for applying international law in Kosovo’s legal order?

The Reception of International Law in Kosovo’s Legal Order: Relevant Provisions of the 2008 Constitution of Kosovo

Although the text of the above cited Article 3(2)(d) KSC Law suggests that Article 19(2) of the Kosovo Constitution gives customary international law primacy over Kosovo’s domestic law, the said constitutional provision is not quite so clear. It simply states:

Ratified international agreements and legally binding norms of international law have superiority over the laws of the Republic of Kosovo.

Looking at the plain text of this article, one can question whether: (i) the expression “norms of international law” is indeed meant to include customary international law; and (ii) by affirming the superiority of such “norms of international law”, this provision also necessarily makes them directly applicable in criminal proceedings in Kosovo. The latter point is particularly important to explain here by using also several examples from other jurisdictions.

Consider, for instance, the situation in the Netherlands, which is one of the most monist states in terms of reception of international law. It has been explained in Dutch scholarship that “[f]ollowing a long-standing customary practice, the Dutch legal order incorporates both treaty and custom”, with Article 94 of the Dutch Constitution then providing primacy for international treaties over domestic laws (Ferdinandusse, pp 66-69). However, the Dutch Supreme Court has recognized an exception to this rule, which establishes that – in the absence of a corresponding domestic law – Dutch courts cannot directly apply CIL rules in criminal proceedings (Zegveld, pp. 99-105). The reason for this is important to point out here: the Dutch Supreme Court defined the legality principle under the Article 16 of the Dutch Constitution narrowly, as requiring that individuals may only be convicted based on pre-existing written laws. This is in contrast to the international definition of legality, which – as recognized and accepted by the European Court of Human Rights – does not require the pre-existing criminal law (national or international) to be written and, thus, allows for convictions based on CIL (Vasiliauskas v Lithuania, paras 154, 171-178; Kononov v Latvia, paras 211-213). Similarly, in Bulgaria, a decision delivered by the Constitutional Court on 2 July 1992 holds that – irrespective of the fact that Article 5(4) of the Constitution makes ratified international treaties directly applicable in the Bulgarian legal order – international criminal law (treaty or customary) cannot be directly applied without a domestic corresponding provision because of the legality principle.

Accordingly, even if Article 19(2) of the Kosovo Constitution is interpreted to generally give customary international law primacy over Kosovo’s national law, it does not automatically follow from this that customary international criminal law is also directly applicable in criminal proceedings in Kosovo. To know this, we need to examine how the legality principle is defined in Kosovo’s constitutional order. If it is defined narrowly, like in the Netherlands or Bulgaria, then the KSC’s ability to apply various rules of CIL directly, as per Article 12 KSC Law, will have to be subjected to a rather crippling limitation: i.e., determining for each CIL norm, which is used to convict an accused, whether it had a pre-existing written equivalent in Kosovo’s law at the time the accused engaged in the indicted conduct.

The legality principle is currently defined in Article 33 of Kosovo’s Constitution from 2008, paragraph 1 of which states:

No one shall be charged or punished for any act which did not constitute a penal offense under law at the time it was committed, except acts that at the time they were committed constituted genocide, war crimes or crimes against humanity according to international law.

Before examining this provision, it is now appropriate to introduce the arguments that the KSC accused have raised to challenge the application of CIL at the Kosovo Specialist Chambers.

Challenging the KSC’s Applicable Law: Veseli’s Arguments

As was pointed out above, multiple accused at the KSC filed jurisdictional motions challenging inter alia the Court’s mandate to apply CIL. For reasons of brevity, this contribution will only focus on the motion filed by Veseli’s Defence, which offered the most elaborate argumentation on this point that was largely also adopted by the other accused.    

The central argument that Veseli puts forward against the direct application of CIL can be broken down in three parts. First, he submits that the relevant constitutional principles which need to be consulted to determine whether CIL can be directly applied in Kosovo’s legal order are defined in the 1974 Constitution of the Socialist Federal Republic of Yugoslavia (‘SFRY’), which was in effect in Kosovo at the material time, not the current Constitution of Kosovo from 2008 (Veseli motion, paras 41, 45). Article 33(4) of Kosovo’s Constitution is cited here, which stipulates that: “[p]unishments shall be administered in accordance with the law in force at the time a criminal act was committed, unless the penalties in a subsequent applicable law are more favorable to the perpetrator”.

Second, Articles 181 and 210 of the SFRY Constitution are cited, which reveal a narrow (and more favorable to the accused) definition of both the legality principle and the acceptance of international law. Specifically, Article 210 SFRY Constitution only recognized international treaties as an applicable legal source in the SFRY’s legal order, stating that:

International treaties shall be applied as of the day they enter into force, unless otherwise specified by the instrument of ratification or by an agreement concluded on the authority of the competent agency. International treaties which have been promulgated shall be directly applied by the courts.

No reference was made to “legally binding norms of international law”, which are additionally included in Article 19(2) of the current Kosovo’s Constitution. Article 181 SFRY Constitution then defined the principle of legality as follows:

No one shall be punished for any act which before its commission was not defined as a punishable offence by statute or a legal provision based on statute, or for which no penalty was threatened. Criminal offences and criminal-law sanctions may only be established by statute. (emphasis added)

The text of this article clearly required that convictions must be based on a pre-existing written law, which thus excluded the direct application of CIL norms that had no corresponding SFRY statutory provision. As pointed out above, such narrow construction of the legality principle is nowadays also adopted in other monist states, like the Netherlands or Bulgaria.

Third, as further support for its submission that the SFRY constitutional provisions are determinative for the question of whether CIL can be directly applied to try individuals for war crimes committed during the Kosovo War, Veseli’s Defence also refers to a series of judgments by the Supreme Court of Kosovo (paras 49-51). In the Kolasinac case from 2003, for instance, that Court applied Articles 181 and 210 of the SFRY Constitution to conclude that:

there can be no direct application of international humanitarian customary law, including criminal liability for command responsibility for omissions, that does not have a basis in the applicable Kosovo criminal law. The constitutional principle of legality presupposes that criminal offences and applicable punishment must be provided for in specific domestic legislation. (Judgment, p. 33, emphasis added)

Based on this finding, the Supreme Court concluded, for instance, that the concept of command responsibility under CIL cannot be fully transferred and applied in Kosovo because it did not have a corresponding domestic provision. According to the judges, Kosovo’s law on criminal omissions could be invoked here, but it would require revising the legal elements of command responsibility to exclude liability for failing to punish crimes and also using a stricter mens rea element than the “should have known”/“had reasons to know”-standard (Judgment, pp. 33-34).

It bears noting here that the case law that Veseli’s Defence cites also includes judgments which were delivered after 2008: i.e., the year when the current Kosovo Constitution came into force. Also, the Defence has cited a judgment by the Constitutional Court of Serbia from 2020, further supporting the conclusion that – under the SFRY Constitution which was in force at the material time – CIL cannot be directly applied today to prosecute events which occurred during the Kosovo War (here, paras 3-8).

One final point merits a mention here. While developing its above-described argument, Veseli’s Defence also made several references to the definition of legality under Article 33(1) of the current Kosovo Constitution. In doing so, the Defence put forward a very unconvincing line of reasoning. It submitted that this constitutional provision is “modelled on Article 7 ECHR and is to be interpreted and applied in accordance with the jurisprudence of the European Court of Human Rights”, which – according to the Defence – allows prosecutions based on CIL only if the indicted CIL offences “were clearly recognized as such at the time of the acts alleged and were given effect in domestic law.” (para This is decidedly incorrect since, as evidenced also in the above mentioned Vasiliauskas Case, the ECtHR has actually found that establishing the CIL-status of an offence at the time the accused committed it can prevent a finding that the legality principle is breached by a state prosecuting that offence on the basis of a domestic law that was passed decades after the accused committed the said crime (Vasiliauskas v Lithuania, paras 154, 171-178).

Upholding the KSC’s authority to apply CIL Challenging the KSC’s Applicable Law: Judge Guillou’s Decision

In his “Decision on Motions Challenging the Jurisdiction of the Specialist Chambers”, the Pre-Trial Judge readily recognized that the application of the KSC Law “must still be in accordance with the constitutional safeguards, in particular the provision on non-retroactivity, enshrined in Article 33 of the [Kosovo] Constitution” (para. 90). Then, after observing that the jurisdictional challenge raised by Veseli questions whether Article 33 of the Constitution, read in conjunction with Article 7 ECHR, prevents the KSC from directly applying CIL norms that did not have a statutory counterpart in SFRY legislation, Judge Guillou reached the following conclusion:

the essence of the provisions of Article 7 ECHR and Article 15 ICCPR, as reflected in Article 33(1) of the Constitution, lies in the authority of the Kosovar legislator to lawfully adopt domestic legislation explicitly providing for international crimes already existing under customary international law at the material time. In so doing, the legislator can allow – or even mandate – prosecution for conduct that took place before the penalisation was introduced in domestic written law. In such cases, there is actually no issue of retroactivity: the legislator is simply transposing (into its own domestic written legislation) crimes that were already part of the legal order, and that were binding on individuals, according to international law, at the time of the alleged commission of the charged crimes. (para. 101)

In essence, Judge Guillou viewed the legality principle under Article 33(1) of Kosovo’s Constitution to have the same scope as the legality principle under Article 7 ECHR. Therefore, in his opinion, the direct application of unwritten laws, like CIL norms which had no equivalent in Kosovo’s statutory laws during the material time, in criminal proceedings would not breach the constitutional principle of legality.

Judge Guillou’s conclusion essentially follows the same line of reasoning that the ICTY adopted in its proceedings: i.e. finding that the ICTY Statute does not establish new crimes but simply gives the Tribunal jurisdiction to apply crimes that were part of CIL during the wars in the former Yugoslavia, which conforms with the legality principle under international law. The underlying assumption that the legality principle under Article 33(1) of Kosovo’s Constitution has the same meaning, however, is not really substantiated by Judge Guillou with any analysis. To this end, support can perhaps be found in Article 53 of Kosovo’s Constitution, which states that the human rights guaranteed in the Constitution have to be “interpreted consistent with the court decisions of the European Court of Human Rights”. However, even here one could argue that this requirement of consistency does not prevent Kosovo’s legislator and courts to construe human rights in a manner that gives individuals even greater protection than the basic standards established by the ECHR: e.g., define the legality principle more narrowly, so as to exclude the possibility of criminal convictions based on unwritten international laws. It seems to the present author that this is a constitutional question with broader implications for Kosovo’s legal order. As such, it ought to be put before Kosovo’s Constitutional Court, over which the KSC has no primacy when it comes to deciding on constitutional matters (Williams, p. 34).

Judge Guillou’s findings also do not really address the essence of the argument that was raised by Veseli’s Defence. As explained above, the core of that argument was not that Article 33(1) of the Kosovo Constitution defines legality in a manner that rejects directly applying CIL in Kosovo’s legal system. Rather, the main point that the Defence raised was that the relevant constitutional provision on legality which applies in the present case is contained in Article 181 SFRY Constitution, which does strictly require that criminal convictions can only be based on a pre-existing statutory provision. Judge Guillou’s only reference to the SFRY Constitution is found in a single paragraph, where he points at Article 3(2)(c) KSC Law to conclude that since this provision makes Kosovo’s domestic laws applicable only if they do not conflict with CIL, “the SFRY Constitution [does] not limit the jurisdiction of the SC in the manner suggested by the Defence.” (para. 99) However, if Article 181 of the SFRY Constitution does indeed provide the applicable constitutional definition of legality in these cases, the fact that the KSC Law is subject to Kosovo’ constitutional safeguards negates the above statement.

One can argue that because the old SFRY Constitution was superseded by the new one, the definition of legality under the old Article 181 – and the afore-cited jurisprudence from the Supreme Court of Kosovo, which rejected the direct application of CIL rules in the absence of corresponding SFRY statutory provisions – is irrelevant: i.e., only Article 33(1) of the current Kosovo Constitution can be the basis of a legality challenge at the KSC. This, however, would still require explaining why the text of Article 33(4) of Kosovo’s Constitution, which demands that convictions are based solely on laws that were in force at the relevant time (unless a newly passed law is more favourable to the accused) does not bring back into application Article 181 SFRY Constitution in the cases falling within the KSC’s temporal jurisdiction. Perhaps it could be argued that Article 33(4) of the Kosovo Constitution is not meant to apply vis-à-vis the said constitutional provisions, but rather refers strictly to substantive criminal laws contained in the various penal codes that have applied in Kosovo over the past two decades. Even so, however, it is very telling that, to the best of this author’s knowledge, when trying persons for atrocities committed in the Kosovo War, not a single court in Kosovo has entered a conviction for crimes against humanity: a category of international crimes which had no statutory equivalent in SFRY criminal law (Dubler and Kalyk, pp 274-275), yet is established under Article 143 of the current Criminal Code of Kosovo. How could that be, if the Kosovo Constitution indeed allows for the direct application of CIL in criminal proceedings, also in cases concerning events that occurred before the Constitution came into force and in the absence of corresponding national legislation that was in force at the material time?


In a Status Conference that was held before Judge Guillou delivered his decision on the motions challenging the KSC’s jurisdiction to directly apply CIL, counsel for the accused Kadri Veseli stated that the issues underlying the questions whether the Court can try JCE, the war crime of arbitrary detention, or superior responsibility, are “not issues that are going to go away lightly” (here, p. 424). It seems very unlikely that the reasoning which the Pre-Trial Judge provided in his decision to confirm an unrestrained mandate for the KSC to apply CIL would put the matter to rest. A much more extensive analysis, which recognizes and carefully considers the relevant provisions of the current Kosovo Constitution – and their interplay with the SFRY Constitution and legislation, accepted also by Kosovo’s other domestic courts – is needed here.

It is beyond the scope of this contribution to explain the legal complexities and practical challenges that would arise if the internationally staffed KSC were indeed required to examine how the legal definition and standards of each crime and mode of liability under CIL compares to their counterparts (if any) under SFRY criminal law. At the same time, it is perhaps helpful to point out that Kosovo’s courts have been quite resourceful in finding a SFRY statutory basis for the application of various CIL norms: e.g., JCE has been considered to have a counterpart in Article 22 (or 26) of SFRY Criminal Code (here, paras 114-115, and here, para xlii), Article 142 of the SFRY Criminal Code has been broadly interpreted to incorporate relevant CIL rules not expressly stated in this provision, including command responsibility (here, paras 111-113), etc. The question remains whether Kosovo’s constitutional safeguards indeed require the KSC to engage in the same comparative analyses that the other domestic courts in Kosovo have been offering when applying CIL, or whether no constitutional restrictions to the application of CIL in criminal proceedings actually exist in Kosovo’s legal order, in which case the KSC Law can be found to properly mandate this Court to directly apply CIL.

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Michael G. KARNAVAS says

August 10, 2021

Excellent analysis. These issues need to be vetted by the Kosovo Supreme Court. Exceptional lawyering by the Veseli Defence, and unsurprisingly, more than a whiff of slight of hand legal reasoning by the Pre-Trial Judge; right out of the ICTY playbook.

Paula Silfverstolpe says

September 7, 2021

Very interesting article!

Actually there has been a conviction for crimes against humanity in a Kosovo Court back in 2001 in the case of Momcilo Trajkovic in Gjilane District Court. It relied on article 37 and 142 of the Yugoslav Criminal Code. The case was handled by the so called hybrid panels during the UNMIK administration (mixed international and local judges) and the presiding judge was a French judge called Patrice de Charette. I know this because at the time I worked as a Legal Officer in the International Judges and Prosecutors program (IJP) in UNMIK DOJ in Pristina. I remember the case raised some debate back then on the question of legality and the SFRY Constitution but not enough to overturn the conviction on appeal. Momcilo Trajkovic was later aquitted on appeal but on other grounds. I attach a link to the judgment in case you are interested.

Best regards,
Paula Silfverstolpe

Lachezar Yanev says

September 18, 2021

Thank you for your kind comments, Michael and Paula!

@Paula, many thanks for sharing this judgment, I read it with much interest. Basically, the judges tried to conjure from the phrase "criminal acts against humanity and international law" in Article 37 FRY Criminal Code, a basis for introducing the notion of crimes against humanity under customary international law in FRY's legal order. The problem is, however, that the said phrase is actually a direct reference to the title of Chapter 16 of the FRY Criminal Code, which exhaustively defined in Articles 141 - 156 what crimes precisely were considered to constitute "criminal acts against humanity and international law" in the FRY legal system. CAH - as established and defined in international law - are just not on that list. Citing Article 142, a provision that is all about war crimes (and expressly starts with "whoever in violation of rules of international law effective at the time of war"), to somehow include "crimes against humanity" in its scope is wrong and conflates these conceptually different categories of crimes.

Then there is the other major flaw, which is that the judges accepted in a single sentence, uncritically and without any analysis, that Article 16 FRY Constitution made customary international law directly applicable in Kosovo's legal order at the material time.

Overall, looking at how extremely tenuous its reasoning for finding a legal basis for CAH conviction was, I am not surprised that this judgment was not picked up in subsequent Kosovo jurisprudence.

Paula Silfverstolpe says

September 20, 2021

Dear Lachezar,

Thanks for your reply. I agree with your comments on the judgement. It was indeed questionable to "squeeze" CAH into the war crimes provisions of the Yugoslav Criminal Code at the time.

It will be interesting to follow the developments at the KSC and especially in the Thaci et al case that has CAH charges. I wonder how it will handle the CAH chapeau requirement of directing a widespread or systematic attack against a civilian population as such. In other KLA case before the ICTY (Limaj and Haradinaj), which largely dealt with similar events in Kosovo, the OTP was not successful in showing that the KLA attacks against political opponents or alleged collaborators fulfilled the chapeau requirement.

Thanks again for initiating an interesting discussion and reflection!