The New Recipe for a General Principle of Law: Premise Theory to “Fill in the Gaps”

Abstract This article proposes a new theory, “premise theory”, to account for recent international criminal courts’ practice on finding general principles of law. After analysing the traditional theory of transposition from national to international legal settings, and the modification/choice model, this article demonstrates that the focus should be shifted from arbitrariness to the determinants of results of recognizing general principles of law. Premise theory explains a mechanism that judges modify a common legal principle or choose the most appropriate national legal principle to apply to the issue at hand to reflect the premises of the legal field, the court, and, sometimes, even the individual case. This article concludes with a proposal for utilizing premise theory as an explanatory tool and as a guide for legal reasoning to increase judicial transparency and predictability. Lastly, it advocates for the application of premise theory to other areas of international law.

Moreover, recent cases have demonstrated that the general principles of law recognized by the International Criminal Court (ICC) differ not only from those in the ad hoc tribunals, 4 but also those from different chambers of the same court. 5 To tackle the traditional but recurring problem of how international courts "fill in the gaps" when there is no clear answer to a question of law, this article explores a new theory to account for recent international criminal courts' practice on finding general principles of law. In other words, it highlights the variables that differentiate the results of recognizing general principles of law. This article confirms the validity of the traditional transposition theory that elucidates the mechanism how national law principles are transposed into international law. Meanwhile, it identifies a gap in this theory and suggests shifting the focus from the mechanism to the factors that determine the contents of a general principle of law. Unlike previous accounts, it argues that the practices of international criminal courts can be theoretically explained as consistent based on a new theory: "premise theory".
This article first highlights the typology problem of general principles of law as they operate in both international law and international criminal law. Second, it examines the existing transposition theory in terms of recognizing a general principle of law that transposes a domestic legal principle into the international legal sphere. Third, it develops premise theory based on analyses of relevant international criminal case law and discusses the implications. This article concludes by proposing the use of premise theory as an explanatory tool and a guide for legal reasoning to increase judicial transparency and predictability, and suggests the application of the theory to other areas of international law.

A. General Principles of Law in International Law
Historically, the general principles of law have been used for inter-state arbitrations since before permanent international courts codified the concept into their statutes. An arbitration process under the Jay Treaty of 1794 and subsequent arbitrations applied domestic private law and Roman law by analogy. 6 This arbitral practice of applying laws that are not based on state consent has been criticised by legal positivists. 7 Many scholars have attempted to explain the practice of applying domestic private law principles and proposed the idea of "universal jurisprudence" which is applicable to any legal relationship. 8 Public international law adopts the concept of such general principles as follows: "[t]he general principles of law recognized by civilized nations" under Article 38(1)(c) of the Statute of the International Court of Justice (ICJ). 9 The concept was first introduced during  6 For example, the parties to the Pious Fund Arbitration of 1893 and the Fur Seal Arbitration of 1902 argued on estoppel and res judicata, respectively, and the arbitrators agreed to apply these principles substantially. See, for example, Arnold D. MCNAIR, "The Legality of the Occupation of the Ruhr" (1924) 5 British Yearbook of International Law 17 at 34-5. 7 Hersch LAUTERPACHT, Private Law Sources and Analogies on International Law (Lawbook Exchange edition: New Jersey: The Lawbook Exchange, 2013, Originally Published: London: Longmans, Green and Co., 1927) at 3-23. 8 Ibid., at 20-31. This explains how analogically applying private law principles from national law to international relations is possible. See the drafting of the Statute of the Permanent Court of International Justice (PCIJ) by writing "the rules of international law as recognized by the legal conscience of civilized nations". 10 The proposal was criticised because it could be treated as an open door for judges to install particular legal values specific to their own national legal systems. 11 Eventually, its current wording was adopted, reflecting the idea that these principles should be "accepted by all nations in foro domestico". 12 Today, it is widely accepted that general principles of law are those that commonly underlie national legal systems. 13 However, scholars' views are split on the typology of general principles of law. The Special Rapporteur of the United Nations International Law Commission has declared the existence of the two types of general principles: general principles of law and general principles of international law. 14 Various scholars have addressed the existence and content of these branches, 15 while some take different views. 16

B. The General Principles under International Criminal Law
The typology problem has been fueled by the development of sub-fields of international law. Although there are only a small number of general principles under international criminal law, all are fundamental and critical. 17 Some scholars have argued that custom has been the basic source of these general principles. 18 However, most of them have domestic counterparts and can also be characterised as general principles of law. 19 The debate is whether the general principles of law applied in international criminal jurisprudence belong in the same category as those applied in public international law.

The Kupreškić taxonomy
The International Criminal Tribunal for the former Yugoslavia (ICTY) 2000 judgment in the Kupreškić case triggered this debate. It distinguished the three types of general principles as applied by international criminal tribunals: (i) the "general principles of international criminal law"; (ii) the "general principles of criminal law common to major legal systems in the world"; and (iii) the "general principles of law consonant with the basic requirements of international justice". 20 In a textbook co-authored by Cassese, who was the presiding judge in the Kupreškić judgment, it is stated that the general principles of international criminal law were defined to "include principles specific to this branch of international law". 21 The authors explained that "the application of these principles at the international level normally results from their gradual transposition over time from national legal systems on to the international order" and "general principles of international criminal law may be inferred from the whole system of international criminal law". 22 In the Kupreškić judgment, Cassese stated that the general principles of international criminal law "may be distilled by dint of construction, generalisation or logical inference". 23 Conversely, the general principles of criminal law, as recognized in domestic legal systems, may be drawn from a comparative survey of the world's principal legal systems. 24 le Droit: Melanges Offerts a Jean Boulouis 139. On the lack of historical background of this dichotomy, see Md Tabish EQBAL, "Historicizing the Dual Categorization of the General Principles of Law by the ILC" (2020) 10 Asian Journal of International Law 187. 17 The number of general principles in international criminal law is limited due to the diversity of sources, divergent definition of the roles of actors, and specificities of each procedural regime.  22 Ibid. It has been noted that while Cassese's position on sources of international law was inspired by a naturalist impulse to protect people, he understood the necessity of the methods of positivism. Robert CRYER, "International Criminal Tribunals and the Sources of International Law: Antonio Cassese's Contribution to the Canon" (2012) 10 Journal of International Criminal Justice 1045 at 1048. 23 Kupreškić, supra note 20 at para. 677. 24 Cassese and Gaeta, supra note 21 at 15.
The Kupreškić judgment stated that "to fill possible gaps in international customary and treaty law, international and national criminal courts may draw upon general principles of criminal law as they derive from the convergence of the principal penal systems of the world". 25 While there is little explanation of the third type of general principles, the existence of the general principles of international criminal law or criminal law are thus presented, and the identifying methodology is provided. However, definitions of these notions, the distinctions between them on a theoretical level, and their legal nature are still unclear. 26 2. The ICC taxonomy Whereas the Kupreškić taxonomy has three categories of principles, the Statute of the ICC identifies two categories; namely, the "principles and rules of international law" (Article 21(1)(b)) and the "general principle of law derived by the Court from national laws of legal systems of the world" (Article 21(1)(c)). 27 Some scholars have noted that, whereas Article 21(1)(b) substantially embraced customary law, clause (c) is a more precise description of the general principles of law, along the lines of Article 38(1)(c) of the ICJ Statute. 28 However, the text and drafting process suggest that the general principles of law defined in Article 21(1)(c) is unique to the ICC procedure. Article 21(1)(c) of the ICC Statute defines the concept as the "general principles of law derived by the Court" (emphasis added), meaning that the ICC has the discretion to derive general principles of law. 29 Furthermore, in contrast to the general principles of law before the ICJ, the ICC is required to include "the national laws of States that would normally exercise jurisdiction over the crime" wherever "appropriate". This phrase was added based on minority opinions from non-Western statesincluding Japan, China, Arab countries, and Israel that the national laws of relevant countries should apply to cases brought before the ICC. 30 The majority disagreed with the application of national law of particular countries. 31 Eventually, the compromise between the two sides took the form of Norway's proposal to insert the phrase "as appropriate", with the caveat that only the "national laws of States that would normally exercise jurisdiction over the crime" would be included. 32 Verhoeven suggested that the drafters might have found it difficult to fully ignore the national law that would be applied by the court, the jurisdiction of which is established 25 Kupreškić, supra note 20 at para. 677. 26 31 Ibid. 32 Ibid.
in accordance with the usual grounds of jurisdiction, such as territoriality or personality. 33 Many scholars have supported the position that the general principles of law defined in Article 21(1)(c) is unique to the ICC procedure. 34 Consequently, at the ICC, the accused may have the opportunity to be processed under laws that they may be familiar with, even when those laws do not belong to the world's major legal systems and include indigenous or religious features. 35 Pellet believed that the specificity of criminal law and the requirements of the nullum crimen principle justify the court deriving general principles of law with no detailed comparative study and prioritizing the legal systems familiar to the accused. 36 The court being required to apply different laws in each case may cause (1)(b) the ICC Statute refers explicitly to the "principles and rules of international law" and thus to customary international law and general principle of law in the sense of Article 38 of the ICJ Statute". Ambos, supra note 29 at 74. 35 Pellet, supra note 18 at 1075. Pellet interprets Article 21(1)(c) to mean that systematic comparison of all national legal systems is unnecessary, and comparative research will be reduced to the family of civil law, common law, and Islamic law. Ibid., at 1073-4. Geōrgios claimed that "national laws of legal systems of the world" means that such national laws "must adhere to a jurisprudential pattern widespread in its application to the extent of qualifying it as a system" and "a system in this context can be contrasted to indigenous or isolated legislation, rule or custom". (1)(c), however, allows the court to apply only principles underlying the national law of the state that would normally exercise jurisdiction over the case and indicates that they can be applied if they are deemed appropriate and consistent with the ICC Statute. Ambos, supra note 29 at 79; Bruno SIMMA and Andreas PAULUS, "Le rôle relatif des différentes sources du droit international public: dont les principes généraux du droit" in Hervé ASCENSIO, Centre de Droit International de l'Université Paris confusion. 37 However, the text of Article 21(1)(c) clearly left the judges broad discretion in determining which national laws to consider in deriving general principles of law. 38

C. Same Origin, Different Generation
The text and the drafting process of Article 21(1)(c) of the ICC Statute highlighted that it allows for the original recognition of general principles of law that are most appropriate for the case and its definition thus differs from that in public international law. Some scholars, including Schabas and Degan, have argued that the source of law defined in Article 21(1)(c) is distinguishable from general principles of law as defined in the Article 38 of the ICJ Statute, 39 and the general principles of law in international criminal law cannot be assimilated into a public international law source. 40 Conversely, others, including Akande and Raimondo, have argued that general principles of law in international criminal law are the same as those in public international law because the origins of the general principles of law and those of international criminal law are both national laws. 41 Disagreements may occur because of different foci. Schabas and Degan concentrated on the already recognized general principles of law found in international conventions and/ or case law, whereas Akande and Raimondo focused on their origin as national laws. 42 Similar to that the same ingredients being cooked in different meals due to the applied cooking methods and spices, the recognition methodology converts the pile of national laws into a new source that has unprecedented features. The next section discusses the existing theory about the mechanism of recognition to examine whether we already have sufficient explanation for such a metamorphosis.

II. Transposition theory: modification/choice model
The prevalent view on the methods of recognizing general principles of law is "first, determining the existence of a principle common to the principal legal systems of the world; second, ascertaining the transposition of that principle to the international legal Ouest-Nanterre-La Défense, Emmanuel DECAUX, and Alain PELLET, eds., Droit International Penal, 2e éd. system" (a two-step approach). 43 The process of adjusting national principles and making them applicable to international trials is called "transposition". 44 Per Ellis, the widely understood transposition methodology involves three steps: identifying a principle common to municipal laws, distilling the principle's essence, and adjusting the principle to be applicable to international legal settings. 45 In contrast to this theory, however, empirical research has revealed that "the ICJ generally asserted the existence of principles in international law irrespective of their correspondence to principles pertaining to municipal law". 46 Meanwhile, as presented below, other international courts have implied their willingness to at least perform their obedience to the theory, but transposition often takes the form of either modification or choice.

A. Transposition in Public International Law
Some scholars have suggested that although general principles of law are common to many legal relationships, some are not applicable to international law because of the international legal system's inherent specificities. 47 Lauterpacht noted that many international arbitration awards relied on the legal principles of national private laws and highlighted several cases in which this approach was deemed impossible because of the characteristics of international law. 48 In contrast, Pellet explored cases in which national law had been transposed onto international law, regardless of the contextual and circumstantial differences, and articulated various methods followed in these cases, such as modifying national laws and choosing specific national laws. 49 In some cases, general principles common to national laws such as the principles of non-retroactivity or succession were accepted with significant modification even when the context in which they are used is very different from their usual environment in domestic law. 50 The modification process transforms, simplifies, or adapts a widely shared national principle so that it applies to international legal issues. 51 The second method, choice, involves selecting a national law principle that is appropriate for the given purpose. 52 For example, the PCIJ applied common law principles 43 Second report on general principles of law by Marcelo Vázquez-Bermúdez, Special Rapporteur, supra note 14, at para. 17; See also Ellis, supra note 3 at 954; Raimondo, supra note 41 at 1; Charles T. KOTUBY, Jr. and Luke A. SOBOTA, General Principles of Law and International Due Process: Principles and Norms Applicable in Transnational Disputes (Oxford: Oxford University Press, 2017) at 18. 44 Alain PELLET, Recherche sur les principes généraux de droit en droit international public (Paris II, 1974) at 272-324; Raimondo, supra note 41 at 58; Kotuby, ibid., at 27; Jain, supra note 2 at 493. 45 Ellis, supra note 3 at 954. See also Raimondo, supra note 41 at 45, Jain, supra note 2 at 493-4. 46 Cheng, supra note 8 at 392. As for the ICJ, Article 9 of its Statute, which requires the composition of the Court to represent "the main forms of civilization" and "the principal legal systems of the world" provides justification. See First report on general principles of law by Marcelo Vázquez-Bermúdez, Special Rapporteur, supra note 14 at note 379. 47 For example, Cheng, supra note 8 at note 14. 48 According to Lauterpacht, the factors that make an analogy impossible are not the inherent specificities of international law but, rather, "the shortcomings of international law as a system of law". For example, duress invalidates a contract but cannot invalidate a treaty. Lauterpacht argued that "analogy fails here so far as international law is an undeveloped law", and "it may safely be said that with the development of international law to a system of law… the analogy will hold with undisputed force". Lauterpacht, supra note 7 at 156, 161-9. Gaja pointed out that general principles that exist only in national law do not necessarily form part of international law. Giorgio GAJA, "General Principles of Law" in Rüdiger WOLFRUM, ed., The Max Planck Encyclopedias of Public International Law (2020), at para. 7. 49 Pellet, supra note 44 at 298-318. 50 Ibid., at 302 and 310. 51 Ibid., at 308. 52 Ibid., at 312. such as estoppel and informal restitution, selectively, for pragmatic reasons. 53 The judges have rarely explained why they chose specific national legal principles in certain cases. The parties have sometimes claimed that factual circumstances such as the absence of a higher authority should be considered. 54 The Court of Justice of the European Communities responded to a claim that the deposit system was contrary to German national constitutional law and that respect for fundamental rights forms an integral aspect of general principles of law, even when inspired by member states' constitutional traditions. 55 Pellet claimed that a pragmatic approach was followed in other cases, presented cases in which national law principles common in only two or three countries were prioritized, and indicated that these principles were in harmony with the community's purposes. 56

B. Transposition in International Criminal Law
Similar transposition theory is accepted by international criminal courts. 57 Judges have often explained their process of comparative research of national laws and the method of either modification or choice when deciding cases.
According to the Furundžija case, when referring to national laws both national legal systems as well as general concepts and legal institutions common to all major legal systems must be considered. 58 In addition, when applying national law the specificities of international criminal procedures must also be considered. 59 Gradoni called the first step in the modification "sampling". 60 The sampling process consists of collecting and comparing relevant national and international laws. It deduces an abstract core principle that appears to be common to both national and international rules through two techniques that, using a mathematical metaphor, can be defined as a "common denominator" and a "common multiplier". 61 The second step is called "falsification" and transforms a common principle obtained through sampling to make it compatible with the legal field to which the principle will be applied. 62 This process makes a highly abstract principle specific enough to be applied to concrete cases. 63 Moreover, several relevant cases in international criminal jurisprudence have adopted the method of choice. There is a substantial gap between the two major legal systems of the world; namely, civil and common law systems, particularly in criminal procedures. This gap has made deducing a common principle for specific legal issues difficult. 53 Ibid., at 317. 54  62 Gradoni, ibid., at 16. 63 Ibid., at 27-8.
Therefore, judges occasionally must choose a national principle and apply it to the legal question before them. 64 In these situations, judges have selected the most appropriate approach that resembles specific national laws that belong to either common or civil law, and have rarely relied on other legal systems. 65 Common law principles have occupied a dominant position in international criminal jurisprudence, attracting criticism from scholars. 66 These critics have argued that this reliance on common law has occurred because international criminal courts have been clearly biased towards a liberal system of criminal justice when identifying general principles of law. 67 Mégret explained the method followed by international criminal courts; namely, adopting national legal traditions as receptors of possible solutions that can be constructively combined, and called it a "pragmatic approach" to determine international criminal procedure. 68 This approach can undermine the claim that general principles have been deduced from all major systems globally. 69 Jain provided a more severe criticism, commenting that the ICTY judges "portray general principles as akin to principles of natural law and logic or as principles inherent in the nature of the international legal system", and claimed that "these versions of general principles pose considerable problems for the legitimacy of an international criminal law regime that purports to be sensitive to the rights of the accused". 70 Jain also evaluated jurisprudence on general principles of law in international criminal law as "chaotic" and believed that it does not satisfy the criteria of formal and material validity and fails to comply with the principle of legality. 71

A. Changing the Focus
An evaluation of the practice of international criminal courts in recognizing general principles of law as either pragmatic or illegitimate presents no scientific explanation of the phenomenon. While adopting transposition theory as valid, this article proposes changing the focus from arbitrariness to the determinant. While transposition theory implies the arbitrariness of the judges to transpose a domestic principle into international adjudication, it does not refer to the factors which directed that transposing decision. This article proposes shifting the focus to the factors that determine the contents of general principles of law. Traditional transposition theory has only highlighted the factors as "specificities" of the "international settings". Advanced research by Biddulph and Newman emphasized that there is no single common methodology for the recognition of general principles of law because each area of international law applies a method suited to its "policy objectives and overall characteristics as a specific area of law". 72 However, the factors considered in recognizing general principles of law may also be different depending on the courts, different chambers in a court, or individual cases.
Judges consider various factors when identifying a general principle of law because they must apply law that interfaces with multiple issues, such as the institutional conditions of the court, legal restrictions, normative values that the court should embody, and practical circumstances that disable or hamper the application. A notion that embraces all these issues can be termed the "premises" of the field, the court, or sometimes even the case in question because they are either factual circumstances from which an international court cannot escape or normative values on which the specific court stands. Judges avoid conflict or undermining these premises by carefully modifying or choosing a general principle of law.
Thus, the process of recognizing general principles of law is materially affected by the premises on which it will be applied. Explaining this mechanism requires a new theory that incorporates the premise concept into traditional transposition theory. As stated previously, this article refers to this theory as "premise theory". The premise theory helps identify the premises that have played a critical role in jurisprudence that recognizes general principles of law. Some of these premises appear to be common in many international courts, regardless of inter-state or criminal adjudication. However, the case law analysis below also indicates that judges of international criminal courts have often adopted premises specific to either international substantive criminal law or procedural criminal law, the court's institutional or procedural framework, or the special circumstances of the case. Although the methods are the same in every case, the results differ because each legal field, court, and case has different premises. The premises specific to the legal field, the adjudicatory body, or the case are the variants that determine the different contents of the same general principle of law.

B. Premises of International Criminal Justice
The premise theory helps identify the premises of international criminal justice common to all international criminal courts. Many cases in the early tribunals uncovered premises inherent in international criminal justice.

Substantive criminal law
Case law that defined core crimes or individual responsibility considered the premises of the international humanitarian and human rights laws that constituted the normative foundation of international substantive criminal law. For example, in the Furundžija judgment, facing the lack of a detailed definition for rape under Article 3 of the ICTY Statute, the judges needed to "look for principles of criminal law common to the major legal systems of the world" to "arrive at an accurate definition of rape based on the criminal law principle of specificity". 73 However, the judges noted the lack of uniformity in classifying forced oral penetration as rape in national laws. 74 The judgment did not clarify which national law criminalized 72 Biddulph and Newman, supra note 13 at 286. 73 Furundžija, supra note 58 at para. 177. 74 Ibid., at para. 182. forced oral penetration as rape, but stated that "some States treat it as sexual assault, while it is categorised as rape in other States". 75 It referred to "the very raison d'être of international humanitarian law and human rights law" and recognized "the general principle of respect for human dignity". 76 The judges concluded that acts of forced oral penetration "constitute a most humiliating and degrading attack upon human dignity" and such acts "should be classified as rape". 77 Thus, the judges chose domestic laws that classify forced oral penetration as rape after considering the premise of international criminal law, which is respect for human dignity.
Similarly, the majority opinion in the Erdemović case, which was heard before the ICTY, considered a value embedded in international humanitarian law to be a premise that directly recognizes one side of national laws as a general principle of law. 78 To find a solution to the question whether duress could be pleaded as a complete defence for a crime against humanity from general principles of law's perspective, the bench studied national laws on duress in the context of killing an innocent person and concluded that there was "no consistent concrete rule". 79 The majority of the judges then believed that it was their mandated obligation to ensure that international humanitarian law was not undermined. 80 Having considered the effective implementation of international humanitarian law as the premise of international criminal law, the majority opinion was that duress cannot afford a complete defence in cases of crimes against humanity or war crimes that involve the taking of innocent lives. 81 This conclusion was explicitly based on an approach under English law. 82

Administration of justice
Because of the importance to the entire world of the mandate to end impunity, the premise of the need for proper administration of justice plays a critical role in identifying procedural principles in international criminal courts. In the Kupreskić judgment, the Trial Chamber of the ICTY dealt with an indictment based on an erroneous legal characterisation of facts. 83 The judges noted that "no general principle of criminal law common to all major legal systems of the world may be found". 84 Therefore, they observed, it "falls to the Trial Chamber to endeavour to look for a general principle of law consonant with the fundamental features and the basic requirements of international criminal justice" and applied the choice method. 85 The chamber identified two major requirements that had acquired paramount importance because of the present status of international criminal law: (i) that the rights of the accused should be fully safeguarded and (ii) that the tribunal should be in a position to exercise all of the powers necessary for it to fulfil its mission efficiently and in the interest of justice. 86 What was described as "a careful balancing of the two aforementioned 75 Ibid. 76 Ibid., at para. 183. 77 Ibid.  79 Ibid., at paras. 38 and 59-72. 80 Ibid., at para. 72. 81 Ibid. 82 Ibid., at paras. 73-88. The non-existence of hierarchy among the core crimes, which is the premise specific to substantive international criminal law, was considered in Prosecutor v. Dragoljub Kunarać, Radomir Kovać and Zoran Vuković, Judgment of 12 June 2002, Appeals Chamber, Case No. IT-96-23 & IT-96-23/1-A at para. 170. 83 Kupreskić, supra note 20, at para. 728. 84 Ibid., at para. 738. 85 Ibid. 86 Ibid., at para. 739.
requirements" led to the conclusion that the prosecutor must request that the Trial Chamber amend the indictment, which was similar to the rules found in the national laws of England and the United States. 87 The need to maintain the integrity of proceedings guided the Special Tribunal for Lebanon's Appeals Panel in a contempt case to choose the principle of corporate criminal liability, which functioned in interpreting the word "person" under its Rule 60bis. 88 The panel claimed that "corporate liability for serious harms is a feature of most of the world's legal systems and therefore qualifies as a general principle of law". 89 It added, "States still differ in whether such liability should be civil or criminal or both". 90 However, it concluded that, "given all the developments outlined above, corporate criminal liability is on the verge of attaining, at the very least, the status of a general principle of law applicable under international law". 91 The "developments outlined above" are actually that "it remains true that no post-World War II international criminal court or tribunal has previously found that it had the authority to try legal persons". 92 The only possible basis for the panel's determination to decide that international criminal law embraces corporate criminal liability was "the Tribunal's inherent power to protect the integrity of its proceedings". 93 Thus, the judges chose national laws that provided corporate criminal liability as a general principle of law applicable to the case before them, considering the premise of the integrity of proceedings.
3. Internationally recognized human rights as a written premise of the ICC Premise theory explains the influence of ICC Statute Article 21(3), which explicitly stipulates the premise of this court on the recognition of general principles of law. The "application and interpretation of law" pursuant to Article 21(3) "must be consistent with internationally recognised human rights" is considered a clear utterance of the premise that is intended to play a critical role in determining an applicable law before the ICC. 94 In the Lubanga case, a stay of proceedings was sought based on the abuse of process principle that is only applicable in England and the Commonwealth, and Roman-Dutch law countries such as South Africa. 95 After assessing relevant and varying domestic laws and cases, the judges declared that the ICC Statute and rules do not leave room for the application of a general principle of law. 96 They shifted to the discussion of human rights and Article 21(3). 97 Considering the right to fair trial to be a basic human right, the judges concluded, "[w]here the breaches of the rights of the accused are such as to make it impossible for him/her to make his/her defence within the framework of his rights, no fair trial can take place and the proceedings can be stayed". 98 Thus, the judges chose to apply the abuse of process principle, which is specific to a limited number of states relying on the premise stipulated in Article 21(3). The approach did not directly recognize the general principles of law but, rather, was a declaration that affirmed internationally recognized human rights. However, the method applied ex facto was the choice method.

C. Premises and Fragmentation
Premise theory reveals the mechanism of the convergence and diversification of general principles of law between different international criminal courts. Different premises sometimes work for convergence. In the Barayagwiza case, the International Criminal Tribunal for Rwanda (ICTR) declared that the application of the abuse of process doctrine protects the "court's integrity" and reached the same conclusion as that in the Lubanga case mentioned above. 99 However, there are more cases in which different premises led the courts to recognize different contents of general principles of law.

The different legal bases of the courts
Unlike the ICC, the ad hoc tribunals have had to adopt an appropriate form of general principles of law due to their unique way of establishment. The judgment in the Delalić case discussed the premise for the ad hoc tribunals when examining the applicability of the legality principle. 100 The court asserted that principle of legality is recognized in all of the world's major criminal justice systems, 101 and adopted the modification method. It first noted that the approach to criminalizing an act differs between national and international legal systems, and then found that the application and standards of the legality principle must differ in international trials because core crimes are prescribed in treaties and/or customary law. 102 The factors to be considered are "the nature of international law", "the absence of international legislative policies and standard", "the ad hoc processes of technical drafting", and "the basic assumption that international criminal law norms will be embodied into the national criminal law of the various States". 103 The bench modified the legality principle to mean that the exercise of the ICTY's jurisdiction is limited to offences already recognized by international humanitarian law. 104 The judgment indicated the premise of international criminal justice and modified the contents of the legality principle where they differed from what was common to national laws. Such premises are not applicable to the ICC which only has jurisdiction over crimes that are codified in its Statute in respect of crimes that were committed after its entry into force. 105 Similarly, the ICTY discussed the principle that courts must be established by law in the Tadić case and considered the premises of the ad hoc tribunals. 106 The defence argued that the ICTY had not been established by law and that its jurisdiction was invalid. 107 The Appeals Chamber compared the three human rights conventions (the International Covenant on Civil and Political Rights, the European Convention on Human Rights, and the Inter-American Convention on Human Rights) and declared that the restriction was a general principle of law. 108 The chamber declared that this principle is applicable to judicial administration in national settings. 109 However, it adopted an "interpretation" that it can be deemed to have been "established by law" when a court grounds it in the rule of law and provides all guarantees codified in relevant international instruments. 110 The judges noted that "the legislative, executive, and judicial division of powers which is largely followed in most municipal systems does not apply to the international setting". 111 Therefore, the judges concluded that the interpretation of the principle "established by law" was that its establishment should be in accordance with the rule of law, which "appears to be the most sensible and most likely meaning of the term in the context of international law". 112 The premises considered in this case are also inapplicable to the ICC, as its Statute is a treaty that is formally recognized as a formal source of international law.

Adversarial or inquisitorial procedure
The structural and normative differences between the ad hoc tribunals and the ICC are demonstrated through different case law on witness proofing. 113 Witness proofing is widely used in the United States but is prohibited in many civil law countries and England and Wales. In Lubanga, the ICC Pre-Trial Chamber found that "if any general principle of law were to be derived from the national laws of the legal systems of the world on this particular matter, it would be the duty of the Prosecution to refrain from undertaking the practice of witness proofing". 114 In a similar vein, Trial Chamber I found that "whilst some aspects of a proofing session could potentially help the Court arrive at the truth in an efficient manner, many others may prove detrimental" and concluded that the preparation of witness testimony would undermine "the spontaneous nature of testimony", which "can be of paramount importance to the Court's ability to find the truth". 115 However, the practice is widely used in the ad hoc tribunals. In the Milutinović case, the ICTY refused to follow the ICC's decision because of the difference in applicable law and practical situations, such as the number of witnesses handled daily. 116 The ICTR in Karamera also declared that witness proofing conforms with established practice, which is useful for the administration of justice. 117 These decisions provide little assessment of the practice's impact on the truth-finding process. 118 Ambos claimed that because the ICC adopts a mixed adversarial-inquisitorial procedure, whereas the ad hoc tribunals follow a predominantly adversarial procedure, the ICC is not compatible with the adversarial origins of witness proofing. 119 The different norms rooted in distinct procedural systems may have constituted different premises that functioned to direct the courts' decisions. 120 3. Case-specific premise Contextual conditions may function as a case-specific premise that alters the contents of the general principle of law that had been adopted by the same court. The ICC's Kenya decisions overruled the Lubanga decision on witness proofing and set detailed rules when allowing this practice, considering that judges are granted "a significant degree of discretion concerning the procedures". 121 The numerous allegations of witness tampering in this case have generally been deemed to constitute the context behind this decision. 122 Trial Chamber V noted specifically that "in the present case, witness preparation is even more crucial as a means to protect the well-being of the witnesses, considering the specific situation in Kenya". 123 It declared that "judicious witness preparation aimed at clarifying a witness's evidence" and "carried out with full respect for the rights of the accused is likely to enable a more accurate and complete presentation of the evidence" and assist the "Chamber's truth finding function". 124 Thus, the premise of the ICC to establish truth influenced both the Lubanga and Kenya decisions to formulate its general principle on witness proofing, but an additional premise of the latter case, namely the need to protect the wellbeing of witnesses, modified the contents of the same general principle of law.
Later, Trial Chamber VI in Ntaganda clarified that decisions would vary based on "a careful review of the circumstances prevailing in each case at the court". 125 With or without such assessment, at the time of writing, Trial Chambers V and VI adopted a witness preparation protocol; Trial Chambers I, III, VII, VIII, and IX decided not to allow such a protocol; and Trial Chambers II and IV did not pronounce on this issue. 126 The circumstances that allow this practice include the "different cultural backgrounds" of witnesses 127 and "significant challenges related to meeting and interviewing witnesses in the field". 128 Thus, the diverse jurisprudence of the different ICC chambers regarding witness proofing shows that the general principle of law can differ depending on the premise of an individual case.

IV. Conclusion
This article has demonstrated that premises have played a critical role in the recognition of general principles of law. The theory focusing on the premises that were considered when recognizing different general principles of law explains why the contents of general principles of law differ depending on the legal field, court, or case. Thus, premise theory offers a new perspective on international criminal courts' practice in recognizing general principles of law. While the international criminal law has been criticized to be teleological in nature, 129 premise theory provides a partial but scientific clarity on the method that has adopted teleological law recognition. It is not merely a discretionary response but a reproducible practice that attempts to respond to premises of international criminal justice, the courts, or the cases.
Premise theory works as an explanatory tool to account for the practice of international criminal courts and may increase predictability as regards the courts' practice of recognizing new general principles of law. When clearly mentioned, the theory allows judges to articulate the premises that function as variables in recognizing a general principle of law. For legal predictability and transparency, judges should explicitly describe the premises that they considered in recognizing specific general principles of law. 130 For prosecutors or counsels, an explicit indication of the premises of the court or the case, including the cultural background, tradition, religious beliefs, or values familiar to the accused or victims will provide strong justification for their claim for applying specific general principles of law to the case at hand. Such use of general principles of law should function as an open door for flexibility that should accompany the multicultural characteristics of modern international criminal courts.
Premise theory should also be applied to explain the method of recognition of general principles of law in other fields of international law. It has been noted that the sources of public international law "reflect the peculiarities of a discipline whose fundamental premise, though evolving, is based on a consensual relationship between co-equal sovereign 125 130 It has been argued that the process of identifying general principles of law should be more transparent and coherent. See Kotuby and Sobota, supra note 43 at 18. Jain also claimed that courts must pay attention to clarifying the basis for material validity and the specific features of international criminal law that reveal an underlying general principle. Jain, supra note 71 at 113. states". 131 Conversely, the liberal premises of international criminal law include juridification, criminalization, and individualization. 132 Considering other fields of international law, European Union (EU) law, for example, may be based on the premise of a single market, which is the basis of the general principles of EU law, such as the principle of integration of the market and free movement. 133 General principles, such as fair and equitable treatment, embody the grundnorm of international investment law. 134 The law of the international civil service is formed through the recognition of general principles such as the independence of international civil servants before international administrative courts. 135 Further research may reveal whether premise theory can explain how general principles of law are recognized in other fields or before different international courts and, conversely, what premises do or can exist in relation to different courts or even individual cases.
The main difficulty encountered in accepting premise theory is the problem of assessing the legitimacy and validity of the premises considered for the recognition of general principles of law. Identifying the premises requires logical persuasiveness and philosophical grounding. The selection of premises often involves value-oriented determination based on either realistic or cosmopolitan views of international criminal justice. 136 Whereas all international criminal justice institutions agree on a set of common goals and pursue them, disagreement regarding priorities result in different international criminal procedures. 137 Furthermore, premise theory allows judges to select different premises on a case-by-case basis, which ICC Statute Article 21(1)(c) explicitly endorses. Thus, the general principles of law as specific rules will not contribute to maintaining the coherence of international law or each field of international law. 138