Article 38(1) of the Statute of the International Court of Justice (ICJ) (the “Statute”), which is almost identical to Article 38(I) of the Statute of its predecessor, the Permanent Court of International Justice, lists as primary sources of international law: (a) international conventions; (b) international custom; (c) general principles of law recognized by civilized nations (principes généraux de droit reconnus par les nations civilisées). With regard to this last category, however, there is no consensus among legal scholars on its exact nature and scope, as well as what distinguishes it from other sources of law. As noted by Professor Bin Cheng, general principles of law have been “the most controversial of the various sources of international law enumerated in Article 38 of the Statute and thus of international law in general”.¹

A debated aspect, for instance, has been the use of the expression “civilized nations” in the context of Article 38(1)(c), which, as pointed out by Professor Gaja, might explain why international courts have so far been reluctant to refer to principles inferred from one or another municipal system.² With regard to this particular issue, however, a presumption exists that this expression is by now redundant and references to civilized nations should be understood to encompass all States.³

A more complex issue concerns the meaning of the term “general principles of law”. While there is a general understanding among scholars and international courts that such an expression refers to those principles common to most domestic legal systems,⁴ the methodology and evidence needed for inducing them from municipal law is controversial.

As recently noted by Professor Ellis, the positivist approach to Article 38(1)(c) of the Statute, although generating consensus, has been often disregarded by international adjudicators, who have asserted the existence of general principles of law based more on natural law assumptions than on a comparative study of domestic legal systems.⁵ International judges have indeed resorted to principles found in foro domestico to validate their reliance on a certain principle, even without undertaking an in-depth investigation into domestic legal systems.⁶

The theoretical ground for such an approach has been well depicted by Judge Shahabuddeen, according to whom general principles of law would not amount to generalizations reached by the application of comparative law but to particularizations of a common underlying sense of what is just in the circumstances; as a consequence, an international tribunal may select an interpretation, even if it is at variance with that of some legal systems.⁷ It is self-evident, however, that a similar attitude might entrust judges with excessive discretion, in breach of the drafters’ intention.⁸

Another controversial aspect is whether general principles of international legal origin (generally referred to as “general principles of international law”) are encompassed within the meaning of Article 38(1)(c) of the Statute.⁹

While some commentators exclude principles of international law from the scope of the recalled provision,¹⁰ several scholars have interpreted it to also—if not primarily—embody general principles of an international character.¹¹

Whereas the travaux préparatoires provide no guidance on this particular issue, several arguments have been put forward in support of the inclusion of general principles of international law within the scope of application of Article 38(1)(c). Professor Lammers, for instance, has noted that, in the light of the ordinary meaning of the terms in Article 38(1)(c) of the Statute, there can be no objection to considering these principles as included in the provision.¹² The term “law” may indeed refer to both national and international law. Similarly, the expression “recognized by civilized nations” would adapt to principles found either at the domestic or international level.¹³ Teleological interpretations would further support the aforesaid conclusion, given that the ratio of the debated notion was to enable the ICJ to deal with lacunae in international customs and treaties.¹⁴

Professor Bassiouni has also stressed that, in light of the differences between the international and domestic legal systems, principles-sources of international law might well emerge in the international legal context without having a specific parallel in national law. In his view, any attempt to exclude these principles from the meaning and scope of Article 38(1)(c) would fail to take into account what amounts to unperfected expressions of other sources of law and would therefore be incongruous with the drafters’ intention.¹⁵

Other authors have subsumed the inclusion of general principles of international law within the meaning of Article 38(1)(c) of the Statute by upholding a unitary approach to the same concept of “general principles of law”. Professor Tunkin, for instance, argued that “general principles of law” are not only those principles common to municipal legal systems but also peculiar to international law.¹⁶ Therefore, for a principle to be considered as falling under Article 38(1)(c), it would be necessary to demonstrate that it also pertains to international law.¹⁷

As previously stated, however, this approach is not unanimous. Besides those commentators arguing that the notion of general principles of law in Article 38(1)(c) refers to general principles of both national and international law, several scholars have asserted that general principles of international law would indeed amount to either treaty or customary law and, accordingly, find their legal basis in Article 38(1)(a) or (b) of the Statute of the ICJ.¹⁸ Other authors even proposed a broader concept of general principles of international law. According to Professor Brownlie, for instance, general principles of international law may be customary rules, general principles of law in the sense of Article 38(1)(c) of the Statute or logical propositions derived from legal reasoning that are based on existing international law and national analogies.¹⁹

Regardless of the above-mentioned doctrinal debate, the ICJ has somehow confirmed that Article 38(1)(c) of the Statute also includes general principles of international legal logic. Indeed, the Court has often referred to principles of international law that do not have a parallel in national legal systems.²⁰

Further, Article 21 of the Statute of the International Criminal Court seems to have upheld the distinction and co-existence of the two categories of general principles by listing, among applicable law, both “general principles of law derived by the Court from national laws of legal systems of the world” and “principles of international law”.²¹

The specific traits of the category of general principles of international law are, however, anything but clear. As it has been correctly observed, an exhaustive enumeration of general principles of international law amounts to a task defying human capacity and, in practice, to a potentially unlimited process.²² Professor Brownlie even asserted the inappropriateness of a rigid categorization of this source, though he noted examples of principles pertaining to it such as, inter alia, the principle of consent, reciprocity, equality of States, good faith, domestic jurisdiction and the freedom of the seas.²³

Although relatively little attention has been paid recently to this particular aspect by legal doctrine, it is undeniable that the autonomy of the international legal system and the transnational dimension of the modern society have increasingly fostered the role of general principles of international law, especially in those areas—such as, for instance, environmental protection—where customary and treaty laws have proved to be defective. These principles have often found recognition in Declarations of principles and other soft law instruments (although a similar circumstance requires a careful distinction with those international rules articulated therein) but might also lack written transposition.

The principle of humanity (often referred to also as “laws of humanity” or “elementary considerations of humanity”)²⁴ is embodied in preambles to international conventions as well as to resolutions of the United Nations General Assembly.²⁵

The Preamble to the 1899 Hague Convention II containing the Regulations on the Laws and Customs of War and Land, for instance, expressly provides that:

Until a more complete code of the laws of war has been issued, the High Contracting Parties deem it expedient to declare that, in case not included in the Regulations adopted by them, the inhabitants and the belligerents remain under the protection and the rule of the principles of the law of nations, as they result from the usages established among civilized people, from the laws of humanity and the dictates of public conscience.²⁶

This provision—named “Martens clause” after its proposer—was restated, although slightly modified, in the 1907 Hague Convention IV on Laws and Customs of War on Land²⁷ and in the denunciations clauses to the 1949 Geneva Conventions.²⁸ In Article 1 (“general principles and scope of application”) of the I Additional Protocol²⁹ and in the Preamble of the II Additional Protocol to the Geneva Conventions,³⁰ the expression “laws of humanity” has been substituted with the term “principles of humanity”.

As observed by legal doctrine, one of the primary merits of this provision has been to approach the question of the laws of humanity for the first time under an (apparently) positivist perspective, rather than a moral one.³¹ That notwithstanding, the clause remains elusive on the content and nature of the “laws of humanity” to which it refers to, as well as to the distinctive elements between the aforesaid notion and that of “usages established among civilized nations”.

International tribunals and arbitrators, as well as national courts, have also often referred to the so-called principle of humanity in their case law.³² Principles of humanity, for instance, were referred to in the High Command Trial held in Nuremberg in the wake of World War II. The Tribunal affirmed that the commanders’ responsibility in occupied territories was established in the customs of war, international agreements, fundamental principles of humanity and the authority of the commander.³³ The Tribunal further observed that:

From an international standpoint, criminality may arise by reason of the fact that the act is forbidden by international agreements or is inherently criminal and contrary to accepted principles of humanity as recognized and accepted by civilized nations.³⁴

Thus, the Tribunal seemed to envisage generally accepted principles of humanity as autonomous source of international law, distinct from both international agreements and customs.

In 1928, the arbitral tribunal in the Naulilaa case applied this principle to limit the legitimacy of reprisal.³⁵ The Tribunal found that reprisal “est limitée par les expériences de l’humanité et les règles de la bonne foi, applicables dans les rapports d’État à État”.³⁶

In its 1949 judgment on the Corfu Channel case, the ICJ found that the obligations incumbent on Albanian authorities to provide notice of the existence of a minefield in its territorial waters and to warn the British ship of the danger were based not on the Hague Convention of 1907, applicable in time of war, but “on certain general and well-recognized principles, namely: elementary considerations of humanity, even more exacting in peace than in war”.³⁷

This passage also echoes in the separate opinion of Judge Álvarez, according to whom the characteristic of international delinquency, as a notion relevant to the damage suffered by a State in the territory of a different State owing to the negligence of the latter, “are that it is an act contrary to the sentiments of humanity”.³⁸

Regardless of the decision’s ambiguous wording, it appears clear from the above that the Court referred to the principle of humanity as a source of legal obligations distinct from treaty law.

The International Court of Justice has further referred to the concept of “elementary consideration of humanity” in subsequent cases. In its judgment in the Case Concerning Military and Paramilitary Activities in and against Nicaragua, the ICJ found that, regardless of whether the United States’ reservations to the Geneva Conventions constituted a bar to their application in the case, the United States might be judged according to the fundamental general principles of humanitarian law.³⁹ To this end, the Court recalled, in particular, that, pursuant to the same Conventions, their denunciation may in no way impair the obligations which the parties should remain bound to by virtue of the principles of the law of nations, as they result from the “usages established among civilized people, from the laws of humanity and the dictates of public conscience”.⁴⁰ The Court further noted that the rules laid down in Article 3, common to all four Geneva Conventions, with regard to armed conflict of non-international character, constitute a “… minimum yardstick, in addition to the more elaborated rules which are also to apply to international conflicts …” and “… reflect what the Court in 1949 called ‘elementary considerations of humanity’”.⁴¹ By means of this reasoning, the Court again seemed to rely on “elementary consideration of humanity” as an autonomous source of international law.

The ICJ’s subsequent case law, however, reveals a different approach.⁴² In both its Advisory Opinions on the Threat or Use of Nuclear Weapons and on the Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory, the Court referred to “elementary considerations of humanity” not as an autonomous source of legal obligations but as an inherent character to humanitarian rules.⁴³

This approach has also been upheld, although in a more nuanced manner, by the ICJ in its judgment concerning the South West Africa cases, where it found that:

Humanitarian considerations may constitute the inspirational basis for rules of law … Such considerations do not, however, in themselves amount to rules of law.⁴⁴

Contrary to the ICJ, the International Criminal Tribunal for the Former Yugoslavia has firmly held that:

Elementary considerations of humanity, emphasised by the International Court of Justice …, should be fully used when interpreting and applying loose international rules, on the basis that they are illustrative of a general principle of international law.⁴⁵

Thus, the Tribunal explicitly attributed to “elementary considerations of humanity” the status of general principles of international law, although it found these principles could not exert any law-making function but only serve as an interpretative means.⁴⁶

However, the Tribunal’s jurisprudence has also proved to be in some way oscillatory. In other decisions, the Tribunal seems indeed to regard at the principle of humanity as a source of law. In the Martič case, for instance, the Tribunal found that the prohibition against attacking civilian population and the general principle limiting the means and methods of warfare also emanate from elementary considerations of humanity, which constitute the foundation of the entire body of international humanitarian law.⁴⁷

In addition to the abovementioned case law, it suffices here to point out that the principle of humanity has also been increasingly referred to in international legal domains different from humanitarian law and human rights law.⁴⁸ To provide an example, the International Tribunal for the Law of the Sea has expressly relied on the aforesaid principle in relation to the use of force in the arrest of ships. More specifically, the Tribunal found that:

Although the Convention does not contain express provisions on the use of force in the arrest of ships, international law … requires that the use of force must be avoided as far as possible and, where force is unavoidable, it must not go beyond what is reasonable and necessary in the circumstances. Considerations of humanity must apply in the law of the sea, as they do in other areas of international law.⁴⁹

It follows from the Tribunal’s reasoning that “considerations of humanity” would amount in and of themselves to sources of international obligations distinct from treaty law. In this respect, therefore, the Tribunal seems to have further confirmed the ICJ’s dicta in the Corfu Channel and Nicaragua cases.

Despite the fact that international arbitrators and courts have greatly relied on the principle of humanity in their case law, there is a certain amount of disagreement concerning its source, scope and function. As it has been noted in doctrinal debates, it is disputed whether this principle amounts to a separate source of obligations in international law, falling within the scope of the notion “general principles of international law”, or to an aspect of public policy, jus cogens, morality or humanitarian law generally.⁵⁰ Accordingly, the first aspect that deserves preliminary reflection is whether the principle of humanity may indeed be regarded as a general principle of an international legal character.

Commentators have described the principle of humanity, as upheld in international tribunals’ case law, variously, as a general principle of international law,⁵¹ a custom,⁵² a secondary source of law or a soft law principle⁵³ falling in none of the above mentioned categories.⁵⁴

These differences in assessing the use made by international courts of the principle of humanity emerge if one takes into account the antithetical views expressed by Professor Waldock and Professor Fitzmaurice as regards the ICJ’s statement in the Corfu Channel case. The former, although stressing the Court’s ambiguity on the point, interpreted the Court’s reference to “elementary considerations of humanity” as part of customary international law. According to him, the fact that the Court mentioned the principle of humanity alongside the principle of freedom of maritime communication and every State’s obligation not to allow its territory to be used in a way contrary to the rights of other States—both belonging to customary law—was sufficient per se to conclude that the Court intended also “elementary consideration of humanity” as being part of customs.⁵⁵ That notwithstanding, it is in some ways indicative of the doubts that this reasoning may raise, especially considering the Court’s express use of the word “principles”, that Professor Waldock himself did not exclude that, in some instances, Article 38(1)(b) and (c) of the Statute of the International Court of Justice may be seen as a single corpus of law. In this respect, general principles of law would constitute a flexible element enabling the Court to better identify customary norms.⁵⁶

Professor Fitzmaurice, on the contrary, regarded “elementary considerations of humanity” as a specific application of the “good neighbor principle”, forming a source of obligations, which “ha[s] neither been expressly assumed nor arise from any specific rules of international law”.⁵⁷

Based on the stand taken by the ICJ in the South West Africa cases, other scholars have instead observed that:

The claim that correctness as a moral principle currently provides for a sufficient condition for the legal validity of certain human rights norms, better accounts for claims made in a number of opinions issued by the International Court of Justice – such as it appeals to elementary considerations of humanity – … than do alternative explanations drawing on custom or general principles of law.⁵⁸

Similar statements place themselves within—and contribute to—the broad debate over the scope of “general principles of international law”. While some authors have argued that this notion would encompass principles—including the prohibition of the use of force, the principle of non-intervention and elementary considerations of humanity—that are customary in nature,⁵⁹ others have firmly rejected a similar approach and support their “autonomous” nature.⁶⁰

Legal scholars’ different approaches to the nature of the principle of humanity well reflect the vagueness and inconsistency of international case law on the point. Nevertheless, there are several elements that might support the argument that this principle, as interpreted by international tribunals, may be regarded as a self-reliant “general principle of international law”, distinguishable from both custom and treaty law.

First of all, the same vagueness of the statements of international courts may be seen as an inherent aspect of the category. As several commentators have stressed with regard to the ICJ, indeed, its decisions are often unclear about the process that has led it to uphold the existence of a general principle of international law.⁶¹ Two sets of considerations—strictly related to the same nature of general principles of international law—can explain a similar ambiguity. First, in certain cases, the principle is so well accepted that the Court would be in no need to demonstrate its existence.⁶² Second, the Court’s reluctance in the elucidation of general principles of international law may serve their same function “by providing the necessary judicial flexibility to gap-fill where necessary”.⁶³ It is clear that similar considerations may be easily extended to the case law  of other international courts and arbitrators.