Author: Lucas Carlos Lima, Raffaela Kunz, Bernardo Mageste Castelar Campos


Required knowledge:

§2.2. Consent §2.3 Enforcement § 6 Sources § 6.1.Treaty Law § 6.2. Customary International Law § 5 Interactions

Learning objectives: Understanding the secondary sources of international law as listed in Art. 38 of the ICJ Statute; understanding the sources beyond Art. 38 of the ICJ Statute and their function; understanding the role the normative production of non-state subjects - such as international organizations - as sources of international law; understanding the role of soft law and scholarly production on the development of international law.

A. Introduction edit

Besides treaty law, customary international law and general principles of law, Art. 38 of the ICJ Statute in a further sub-paragraph lists "subsidiary means of international law", namely judicial decisions and "the teachings of the most highly qualified publicists of the various nations". The word "subsidiary" has been interpreted by most authors as meaning that judicial decisions and teachings are not formal sources themselves, but rather serve as evidence of the existence of the three formal sources.[1] In light of this, it has been argued that the term "auxiliaire" used in the French version more adequately describes the function of jurisprudence and doctrine.[1] Rather than providing guidance in a subordinate way if the formal sources give no clear answer, these two means serve as tools to elucidate the existence of norms of international law.

However, it is recognized today that the distinction between formal sources and subsidiary means is not as clear-cut as it might seem. For example, while judicial decisions are only listed as "subsidiary means", it is becoming increasingly recognized that in light of the indeterminacy of the law, international norms only come to life once interpreted by courts. Indeterminacy not only refers to the fact that international legal obligations are often phrased in vague terms, leaving room for divergent interpretations. More fundamentally, language as such is indeterminate, and meaning is only established through interpretation.[2] In this sense, judicial decisions undoubtedly play a considerable role in the clarification and thus also the making of formal international law.[3]

It is well-established today that the "list" contained in Art. 38 of the ICJ statute is not conclusive and that further sources of law beyond Art. 38 exist. This is especially the case for soft law, which plays an ever greater role in today's globalized and multi-polar world order. Also acts of international organizations, so-called "secondary law", are increasingly relevant. Besides these sources, unilateral declarations have come to be recognized as further sources beyond Art. 38 ICJ Statute.

B. Subsidiary Statutory Sources (Art. 38(1)(d) ICJ Statute) edit

I. Judicial Decisions edit

1. Judicial Decisions as sources of law edit

When an international court or tribunal renders a judicial decision, it becomes binding upon the parties to the dispute. While the bindingness of a specific judicial decision can be traced to the consent given by the parties to the adjudicative body, the general obligation to respect judicial decisions stems from the pacta sunt servanda principle. In this sense, an international judicial decision creates lex inter partes (law between the parties). The extent to which that decision is capable of creating law for the community as a whole is open to discussion. Since international judicial decisions are currently an unavoidable part of the judicial legal system and might perform distinct functions within different legal regimes (e.g. trade law, human rights law, international criminal law), it is not possible to generalize the role of decisions as sources of international law. As a member of the International Law Commission aptly put it “[t]he weight of judicial decisions and scholarly works vary, depending on the tribunal and relevant field of international law.”[4]

To understand the role international judicial decisions play in the international legal order, this section shall investigate the role relegated to them in the Statute of the International Court of Justice and other normative international instruments (2.); how international courts employ judicial decisions in their reasoning (3.); the way in which the International Law Commission employs international judicial decisions in its recent projects to identify sources of international law (4.) and; finally discuss the existence of the rule of precedents in international law (5.).

2. The normative approach of Art. 38, 1., d) of the ICJ Statute: subsidiarity in relation to other sources. edit

The Advisory Committee of Jurists responsible for drafting the Statute of the Permanent Court of International Justice had to face the question of which position judicial decisions should occupy. Baron Descamps’ proposal to include “international jurisprudence as a means for the application and development of law”[5] as applicable law was ruled out and, instead, judicial decisions were put together with the teaching of publicists in a secondary position.

Article 38(1)(d) of the Statute of the International Court of Justice prescribes that the Court, whose function is to decide in accordance with international law, shall apply judicial decisions as subsidiary means for the determination of rules of law. Additionally, the subsidiary application of judicial decisions in relation to the other three main sources envisaged in Article 38 (treaties, custom and principles) is subject to the provisions of Article 59, which sets forth that the decision of the Court “has no binding force except between the parties and in respect of that particular case".

In a legal order predominantly characterized by decentralized methods of normative production, it is not surprising that judicial decisions occupy a prominent place of importance, despite its subsidiary place in Article’s 38 order. While it is true that “the Court, as a court of law, cannot render judgment sub specie legis ferendae[6], or anticipate the law before the legislator has laid it down”, on several occasions judicial decisions might be influential in shaping the law in a certain field.

The expression “judicial decision” present in Article 38 has been broadly interpreted. While, in the past, the predominance of the International Court of Justice has prompted a debate on the weight of its decisions, the multiplication of international courts and tribunals has added layers to the debate. Moreover, it seems to be an agreed interpretation of that rule that it also comprises decisions rendered by municipal courts to the extent that they are “subsidiary means for the determination of rules of law”. As we shall examine later, decisions of municipal courts are particularly relevant as an element of state practice, one of the two elements of customary rules.

Much has been written on the importance of Article 38(1)(d) of the Statute of the International Court of Justice to frame the debate on the importance of judicial decisions as sources of international law. Other normative indications can be hardly found in the rules of other international courts and tribunals[7][8].[9] A rare exception is Article 21(2) of the Rome Statute of the International Criminal Court, which establishes that “the Court may apply principles and rules of law as interpreted in its previous decisions”. While a more flexible rule in comparison with Article 38(1)(d) of the ICJ Statute, Article 21(2), which is a much more recent rule, also puts emphasis on the fact that the previous decisions are interpreters of rules and principles and not sources per se. Nonetheless, this normative indication reveals a trend within international courts and tribunals: the importance that previous judicial decisions possess in relation to the own case-law of a court and tribunal.

While this lacking normative guidance on the role of decisions reinforces the subsidiary character of judicial decisions as mere tools in the identification of the more classic rules of international closely associated to the consent of States (treaties, customary law, principles), this perception might be wrong. The multiplication of judicial instances and their different functions in international society might suggest otherwise. As put by an author, “there has long been no room for doubt that international law has become very much a case law.”[10]

There has even been some scholarly discussion concerning whether judicial decisions are formal sources of international law. The answer varies according to one’s own conception of the legal field. While to some a negative answ<!er is easily defensible[11], more nuanced approaches such as “quasi-formal”[12] sources might appear, with different degrees of normativity being attributed to judicial decisions, depending on the field in which they appear. Less discussable is the fact that judicial decisions might be highly authoritative[13] within the international legal discourse. Treaties, custom and general principles, when interpreted or applied by international courts, can create obligations to States and other subjects of international law. Unless action is taken to the contrary, the application or interpretation of a rule made by an international court tends to assume the more recent understanding of such a rule. While States, International Organizations and other subjects might disagree with a judicial decision, it is binding upon the parties and serves as a guide to the other members of the community as the most appropriate way to perceive the rule. 

3. Judicial decisions in the practice of international courts and tribunals edit

3.1. Do international tribunals use judicial decisions authoritatively? edit

An important field of observation to understand the authority of judicial decisions is international litigation. In other words, a good means for identifying the legal value of judicial decisions is to observe the importance attributed to them when a court or tribunal settles a dispute between subjects of international law. Other indications may be equally important. For instance, evaluating the influence or impact of a certain judicial decision in the work of codification performed by the International Law Commission[14], the practice of States, or eventually how certain decisions were transformed into treaty law. An illustrative example in this regard can be found in the field of the Law of the Sea, in which the International Court of Justice was considerably influential in some areas such as maritime delimitation.[15] Be that as it may, it is not always possible to identify areas which clearly developed an account of judicial decisions. Given that international courts and tribunals are often called upon to apply international law, the use of international decisions by international courts can be a relevant indication of the value of their authority. There could even be instances where judicial decisions exert more subtle, informal influence on the legal field, irrigating debates or forming a repository of arguments that become unavoidable to understand the develoment of a certain field of international law.

A perusal on the jurisprudence of international courts will reveal the tendency of judicial bodies to refer authoritatively to their previous decisions. They do so either to reinforce the interpretation of a given rule or as a shortcut to the legal reasoning previously espoused. In both cases, the court or tribunal contributes to the consolidation of such a rule, apart from the possibility of developing the content of the law.

The high reference to its own jurisprudence by international courts, and in particular to the International Court of Justice, raised the question of the existence of the rule of mandatory precedent, the rule of stare decisis, as one of the rules of the international legal order. However, in the current state of international law, there do not seem to be any elements that confirm the existence of this rule.[16] International courts and tribunals are not bound to follow their own decisions. Despite this, the International Court of Justice has adamantly recognized in 2015 that

“To the extent that the decisions contain findings of law, the Court will treat them as it treats all previous decisions: that is to say that, while those decisions are in no way binding on the Court, it will not depart from its settled jurisprudence unless it finds very particular reasons to do so”.[17]

This passage is revealing for at least three reasons. First, it seems to confirm that is not the decision per se that constitutes a source, but the “findings of law” that it renders. Second, the Court confirms the non-existence of the stare decisis rules since the decisions are “in no way binding”. At the same time, the Court seems to establish a presumption that its previous decisions will be followed if there are no compelling reasons that lead it to diverge from its past decisions. This presumption can be justified on different grounds. On the one hand, there is the assurance to future litigants that similar situations will be treated similarly. Such approach reaffirms important legal values ​​such as predictability, clarity and, to a certain extent, uniformity and consistency of international law. Overall, the protection of these values ​​reinforces the legitimacy of an international court and the perception that the equality of the parties is fully preserved. This might be a good explanation why different international courts follow a similar path of self-reference and reverence to their previous decisions or even decisions of other international courts.[18]

3.2. Is there a distinction in legal value between decisions of international courts? edit

Although the presumption that decisions of international courts will be relied upon in the future, unless particular reasons prompt the court or tribunal to go a different direction, some questions emerge from this practice of self-reference regarding previous decisions. A first question is whether all judicial decisions have the same impact on the international legal order. A second question regards the contribution of decisions of international courts to shaping the specific field where they are situated.

Since every international court and tribunal was designed with a unique purpose and according to specific contextual and social needs, the decisions they render do not carry the same weight. In this regard, there appears to exist a presumption that a certain tribunal's first duty is to pay tribute to its own case-law before looking beyond its premises. Nonetheless, recent times have witnessed a greater use of external precedents by international courts, a phenomenon frequently called as cross-fertilization. The reference to the case law of other courts seems to obey a logic of speciality, meaning that the specific function of a judicial body places it in a privileged position for the identification, application and interpretation of certain rules. In this regard, the International Court of Justice has observed that

"[w]hen the court is called upon […] to apply a regional instrument for the protection of human rights, it must take due account of the interpretation of that instrument adopted by the independent bodies which have been specifically created, if such has been the case, to monitor the sound application of the treaty in question."[19]

The speciality criteria can illustrate why certain courts refer to others. It offers a presumption of unity in the international legal system. Even though each international court and tribunal remains the master of its own case-law' interpretation, other judicial bodies are free to resort to "external" jurisprudence in order to decide the disputes they are called to. It is no overstretch to affirm that the phenomenon of cross-fertilization has acted as a counterforce to the tendencies of fragmentation in international law, since it is highly capable of promoting harmony between international courts on very specific and often contentious issues. Earlier jurisprudence of a given tribunal may inform future judges of other courts when deciding disputes involving similar factual backgrounds or the ascertainment and interpretation of the same norms. A clear example is the use of regional human rights courts' case law by the International Court of Justice when it is called on resolve disputes relating to human rights.[20] In these situations, the findings of the "external" case-law are applied directly as a secondary source of international law, i.e. as authoritative statements of what the law is.

Finally, not only substantive issues are liable to be the object of cross fertilization between courts and tribunals, but also procedural ones. Procedural practices or principles regarding the delimitation of jurisdiction, the conduction of ancillary proceedings or the behavior of the parties are often developed by international courts and tribunals through case-law, to the extent the whole of the procedural rules guiding their activities cannot be found in their constitutive statutes. This situation reveals not precisely the import of legal "findings" of an external case-law, but a recognition of certain judicial practices as legal rules binding the court given their compatibility with statutory norms and other sources of procedural law (rules of procedure, for instance)[21].

It continues.

4. Decisions of Municipal Courts edit

Paragraph 1 (d) of Article 38 of the Statute of the ICJ does not differentiate between decisions of international courts and municipal courts as subsidiary means for determining the rules of international law. As mentioned in Section B, judicial decisions in general may be considered as a subsidiary source of law and as means for the identification of other sources of law[22]. Although those two characterizations may be recognized both concerning decisions of international courts or tribunals and decisions of municipal courts, there are some particularities of the latter which may be observed in considering them as sources of international law.

4.1. Decisions of Municipal Courts as Subsidiary Sources of International Law edit

As explained in Section 2, judicial decisions may act as a formal source of law creating international obligations for different actors depending on one’s conception of the legal field. Although there are debates regarding the possibility of recognition of decisions of international courts as formal sources of international law, this possibility increasingly reduces regarding decisions of municipal courts due to their national rather than international character. Contrary to decisions of international courts, those of municipal courts can rarely create obligations binding other States and international organizations, partly due to the rules of immunity (see immunity chapter).

On the other hand, decisions of municipal courts may act as formal sources in two situations. In the first situation, decisions of municipal courts may be binding regarding other actors of international law, such as individuals, non-State actors, movements of national liberation and transnational companies. In certain cases, national courts found that obligations under international law were attributable to such actors.[23] Therefore, decisions of municipal courts may have different degrees of normativity or authority in international law.[24] In the second situation, decisions of municipal courts may be considered both as forms of State practice and forms of evidence of acceptance as law (opinio juris) in the identification of a customary rule of international law. In this situation, the municipal decision would not be a formal source per se, but part of the elements of the formation of a customary rule of international law which may be considered together with other elements.

In the Jurisdictional Immunities of the State case of 2012, the International Court of Justice considered that judgments of national courts would have particular significance in order to determine the existence of an international custom conferring immunity on States and the scope and extent of such rule. Such decisions were not analysed alone but considered together with statements made by States in the International Law Commission and during the adoption of the Convention on Jurisdictional Immunities of States and Their Property as relevant State practice.[25]

In addition, decisions of municipal courts might also be authoritative within the international legal discourse in several areas. For instance, cases such as the Schooner Exchange (1812) of the United States Supreme Court, Reference Re Secession of Quebec (1998) from the Supreme Court of Canada, and In Re Pinochet (1999) from the House of Lords of the United Kingdom are often mentioned in the legal literature to refer respectively to exceptions to the rule of sovereign immunity, the content of the right of self-determination, and the existence of universal jurisdiction.

4.2. Decisions of Municipal Courts as Means for the Identification of Other Sources of Law edit

Judicial decisions may also be considered as means for the identification of other sources of law, acting as material sources. This is the case of the identification of customary rules of international law. As recognized by the ILC in Draft Conclusion 13 on the identification of customary international law adopted in 2018, decisions of national courts might be useful as a subsidiary means for determining the extent and content of rules of customary international law. A similar role is found regarding the determination of the existence and content of general principles of law, as recognized by the draft conclusions adopted provisionally by the ILC on the matter in 2023.[26] This is not the same thing as to affirm that decisions of municipal courts are able to "create" international law. Rather, they are vehicles to necessary elements for the recognition of customary law - state practice and opinion juris - and, as a consequence, they can contribute to the identification of an emergent rule of customary nature if their content resonates other samples of practice which, in toto, amount to sufficient consensus concerning its legal character. The role of decisions of municipal courts is even further enhanced when it comes to the identification of general principles of law, since their very conceptual framing encompasses the "recognition" by municipal legal orders. In other words, general principles of law are principles recognized in virtually all municipal legal systems - such as res judicata, estoppel or good faith - and, because of their general recognition by municipal courts , they are also recognizes as sources of international law.

The relevance of the role of decisions of domestic courts in the identification of rules of customary international law is inferior to those given to the decisions of international courts. According to the ILC, this occurs because:

National courts operate within a particular legal system, which may incorporate international law only in a particular way and to a limited extent. Their decisions may reflect a particular national perspective. Unlike most international courts, national courts may sometimes lack international law expertise and may have reached their decisions without the benefit of hearing argument advanced by States.[27]

In this sense, priority is given to decisions of international courts over decisions of municipal courts in the determination of the existence of an international custom. In the Lotus case, for example, the Permanent Court of International Justice only considered decisions of domestic courts after recognizing that there were no international decisions to assist in the recognition of the existence of an international norm dealing with the criminal jurisdiction of States in cases of collisions in high seas.[28]

A different weight is given in the determination of the existence and content of general principles of law common to the various legal systems of the world. The assessment of decisions of national courts is considered part of the comparative analysis of national legal systems necessary to determine the existence of a general principle of law. Nevertheless, as recognized by Draft Conclusion 5 on general principles of law adopted provisionally by the International Law Commission in 2023, this element should be considered together with the assessment of national laws and other materials.[29]

There is also differences between different types of decisions of municipal courts. Decisions of higher courts which may be considered final may have greater weight than decisions of lower courts in the identification of other sources of law.[30] In the Arrest Warrant case, for instance, the ICJ analysed specifically decisions of national higher courts, such as those of France and the United Kingdom, as State practice in order to consider the existence of exceptions to the immunity from criminal jurisdiction to Ministers of Foreign Affairs, together with national legislation.[31]

II. Teachings of the Most Highly Qualified Publicists edit

Art. 38(1)(d) lists "the teachings of the most highly qualified publicists of the various nations" as second subsidiary means to identify the content of international law. Today rather than the word "publicists", the term "scholar" would be used. Often, the literature makes a clear-cut distinction between law-making and scholarly writing. In this view, the role of those writing about international law, as opposed to those making the law, is limited to systematizing and providing a better understanding of the law. As one scholar put it, "(i)t is obviously not a question of 'doctors' dictating the law, but of their influence on its better understanding."[32]

Yet, in reality, the line between law-making and scholarly writing – and in general, between formal and informal sources of international law – is probably not as clear-cut. It is true that today scholars do not hold anymore the place they held historically. In times when the formal sources of international law were much less well documented, scholars played a central role in gathering legal materials, and by doing so arguably also in separating between the law and the non-law. With the increasing availability of state practice and legal materials in other ways, this role became much less relevant.

Nonetheless also today the influence of scholars on international law should not be underestimated. This might be particularly obvious in newer or evolving fields of international law, such as the law applicable to cyberspace, where many legal questions are unsolved and courts and other actors applying the law thus turn to the existing literature for guidance and clarification. Another example of the influence of scholars is when they act in collective bodies and expert groups, sometimes even with a mandate by states.[33] A famous case in point is the International Law Commission (ILC), established by the UN General Assembly, whose task is "the progressive development of international law and its codification" (Art. 1 of the statutes of the ILC).[34] According to Art. 2(1) of its statutes, the ILC shall consist of "persons of recognized competence in International law", which in practice has often included scholars. Some of the work done by the ILC has proven to be highly authoritative and influential, such as the famous Articles on the Responsibility of States for Internationally Wrongful Acts which today provide the starting point for most discussions on state responsibility.[35] Examples of non-state sponsored expert groups who proved to be highly authoritative include the group who drafted the San Remo Manual on International Law applicable to Armed Conflicts at Sea or more recently the Tallinn Manual on the International Law Applicable to Cyber Warfare, and the so-called Tallinn Manual 2.0 on the International Law Applicable to Cyber Operations, published in 2013 and 2017, respectively.

Time and again attempts were undertaken to "measure" the influence of scholars on international law. One method to do so is to look at citations by international courts. However, this method is not particularly reliable.[36] For example, the International Court of Justice only rarely cites scholarly writings, but there is broad agreement that the influence of scholars on the "World Court" is greater than it appears.[1] The same is certainly true for other courts and institutions. More important than the direct reception, citation and influence of scholarship are the manifold indirect ways in which scholars shape and contribute to international law. This begins in the classroom where scholars teach future practitioners, but scholars certainly also exert a certain influence by criticizing, systematizing and ordering the body of international law – a role that has been described as one of "grammarians" within the international legal system.[37]

In light of the relevance of scholarly writings in the creation of International law, it is increasingly being seen as problematic that scholars situated in the West dominate the international legal discourse. While this is particularly obvious when looking at the history of international law, in which the dominant jurists were nearly exclusively European (see history chapter), this still holds true today. The most renowned publishers and journals undoubtedly are European or American. Anthena Roberts has empirically shown that Western (and in particular Anglo-American) institutions and publication outlets such as journals and textbooks dominate the international legal discourse.[38] She not only concludes that Oscar Schachter's famous description of the professional community of international lawyers as "invisible college of international lawyers"[39] is inaccurate, but even fundamentally puts into question whether international law is truly international, as the title of her book suggests. In this sense, the claim to decolonize the knowledge production is not only a historical endeavor with the goal to lay bare the colonial legacies of the accumulated knowledge, but also pointing to the asymmetries in the system of knowledge production continuing until today.[40]

C. Sources Beyond the ICJ Statute edit

I. Soft Law edit

Introduction edit

The term "soft law" refers to those norms in the international legal order that lack legal bindingness. It thus not only falls outside of the category of Art. 38 of the ICJ statute; it seems to fall outside of the category of law as such. Yet, it is undeniable that soft law does have a function and role in today's international order - and arguably increasingly so. According to a narrow definition, soft law can only emanate from subjects of international law, whereas a wider definition also includes instruments such as codes of conducts from actors with not entirely clear status, such as corporations or NGOs (see subjects and actors chapter). Examples are numerous and include non-binding recommendations and resolutions of International Organizations, including the resolutions of the UN General Assembly, and codes of conduct adopted by states or International Organizations, such as the UN Guiding Principles on Business and Human Rights.

Legal effects edit

Despite lacking legal bindingness stricto sensu, it is well recognised that soft law has certain legal effects.

Legal effects. Certain legal effects - states can not invoke the principle of non-intervention; issue areas regulated by soft law do not fall anymore in the "domaine réservé" of states. Furthermore guideline for interpretation; evidence of opinio iuris?

Importance beyond legal effects edit

However, there is today broad agreement that norms can have normative value and effects without being binding in a strict sense. An important point of

Functions: somewhat a compromise between the need to regulate behavior and state sovereignty (MPEPIL par. &); less costly for states; first step on the way to "hard" law; adaptation of international law to new developments. More flexible than hard law and easier to achieve. However, see against the progress narrative: Alonso Gurmendi Dunkelberg, Soft Law in Jus in Bello and Jus ad Bellum: What Lessons for Business & Human Rights?, 114 ajil unbound 174 (2020).


categories: resolutions, inter-state agreements expressly excluding binding force

II. Acts of International Organizations edit

1. Acts of International Organizations as a Distinct Source of International Law edit

Acts or resolutions of international organizations are often listed among possible sources of international law besides the traditional categories of sources recognized by paragraph 1 of Article 38 of the Statute of the International Court of Justice. This consideration reflects the growing importance of the activities and acts emanated from international organizations (see section 'International Organizations'). New procedures of collective action within the framework of international organizations have been developed by the international community in an approach similar to the law-making process of domestic law. Such procedures usually involve a new regulatory approach which goes beyond the traditional law-making process recognized by international law.

For instance, the UN Security Council seems to have adopted a new form of procedure creating general obligations for all States in order to prevent the commission or the financing of terrorist acts, as observed in Resolution 1373 (28 September 2001). This procedure departs from the organ’s traditional powers by not being limited to a concrete situation and has its acceptance explained by the international context of the fight against acts of terrorism caused by non-State actors. The normative force and legitimacy of such kind of act must be understood considering elements such as the activity regulated, the actors involved and the power structures behind it, aspects analysed by the global administrative law.

It would be possible to consider, therefore, that a new way of creating international rules beyond the classic means could have emerged from the operation of international organizations, especially the United Nations. On the other hand, such characterization presents some problems.

1.1 Acts of International Organizations as Formal Source of International Law edit

Acts of international organizations may be considered as a formal source of rights and obligations depending on the actor concerned. Despite the plurality of the classification of legal instruments that international organizations are empowered by their constitutive instruments to adopt, it is possible to differentiate two general types of acts emanated from international organizations regarding their addressees. The first type of instrument consists of acts which are created by organs of the organization usually directed to States or other organizations, therefore having a subject external to the structure of the organization. Such acts may be recommendations, declarations or decisions with binding force or not. The second type of instrument is composed of measures adopted internally by organs of the organization in the fulfilment of their functions as established by the constitutive instrument, determining for instance the budget of the organization, the creation or composition of an organ and other procedural aspects. They are addressed mainly to organs or agents that are internal to the organization’s structure and do not concern inter-State relations. As this second type of act may establish rights and obligations in the internal law of organizations for different organs, individuals and entities, it may be considered a formal source of law for such actors. This is the case of the decisions of the United Nations Dispute Tribunal, which are binding upon the parties of disputes opposing individuals and the UN Secretary-General or a specialized agency.[41]

Regarding the first type of instrument, it is possible to question whether resolutions of international organizations may be considered as a distinct formal source of international law creating legal obligations for the parties concerned (see section 'the Concept of a 'Source' of International Law', subsection 'Categories of Sources?'), since such acts usually have their legal force based on the provisions of the constitutive treaty of the international organization. Member States are obliged to comply with binding resolutions by virtue of an obligation assumed through the constitutive treaty of the international organization, not because such resolutions create direct obligations for them. This is the case of decisions of the UN Security Council based on Article 25 and Chapter VII of the UN  Charter and some acts emanating from the European Union based on Article 288 of the Treaty on the Functioning of the European Union. In this sense, it could be argued that the normative force of resolutions of international organizations is linked to conventional obligations created by treaties, a traditional source of international law.

It is claimed that the UN Security Council on some occasions had adopted a sort of 'law-making procedure' by imposing general obligations to all UN Member States regarding specific matters. In general, the organ adopts decisions binding on the UN Member States which are instrumental to deal with a situation characterized by it as a threat to the peace, a breach to the peace or an act of aggression, according to Article 39 of the UN Charter.[42]

Example for Regular Resolution of the UN Security Council: The Security Council recognized in Resolution 1973 (17 March 2011) that the situation in Libya constituted a threat to international peace and security and decided to adopt binding measures such as the obligation of the Member States to freeze the assets of Libyan authorities and not to allow any aircraft owned or registered in Libya to overfly their territory.


Nevertheless, the Security Council seem to have imposed on the Member States obligations of abstract nature in some resolutions which are not limited to a particular situation or dispute.

Example for Resolutions of the Security Council establishing General Obligations for UN Member States: The above-mentioned Resolution 1373 (28 September 2001) sets out general obligations for States concerning international terrorism and contains obligations under specific international treaties, in particular the obligations to suppress terrorist acts and the financing of terrorist acts established by the Convention for the Suppression of Terrorist Bombings (1997) and by the Convention for the Suppression of the Financing of Terrorism (1999). Similarly, Resolution 1540 (28 April 2004) contains obligations which may also be found in the Treaty on the Non-Proliferation of Nuclear Weapons (1968), the Biological Weapons Convention (1972) and the Chemical Weapons Convention (1993). By Resolution 2396 (21 December 2017) the Security Council establishes the obligation of Member States to adopt measures according to the International Civil Aviation Organization (ICAO) standards and recommended practices on the treatment of passenger data.


In such cases, the Security Council appears to impose on Member States obligations that are found in conventions to which they have not necessarily expressed their consent. Since such obligations have general application and are not limited to a particular situation or dispute, they appear to have been the result of a law-making process by the Security Council. Yet in this case, the resolutions do not act as formal sources of obligations since their binding force is based on the action of the Security Council under Chapter VII of the UN Charter, although their legality in relation to the Charter and the powers of the Security Council may be questioned.[43]

1.2 Acts of International Organizations as Material Source of International Law edit

It is also possible to consider resolutions of international organizations not as a formal source of obligations but as evidence of the existence of an international rule, since the consent by States parties to a resolution may indicate that a given provision is understood to be a norm of customary international law. In this case, resolutions of international organizations may function as a material source of international law (see section 'the Concept of a 'Source' of International Law', subsection 'Categories of Sources?').

Resolutions of the UN General Assembly are occasionally analysed by the International Court of Justice in order to determine the existence of a rule of customary international law. The Court considered that although not binding, UN General Assembly resolutions ‘may sometimes have normative value’ since they ‘can, in certain circumstances, provide evidence important for establishing the existence of a rule or the emergence of an opinio juris’.[44]  Such an approach was adopted in the Nicaragua case of 1986, in which the consent of the United States and Nicaragua to UN General Assembly Resolution 2625 (24 October 1970, establishing the Declaration on Principles of International Law concerning Friendly Relations and Co-operation among States in accordance with the UN Charter) was understood by the Court as an acceptance of the validity of the rules declared by the document.[45]

Although not formally binding on its Member States, resolutions adopted by the UN General Assembly are sometimes considered to reflect legal rules of international law due to the almost universal representation of the international community of States in the organ. This is the case of the Declaration on Principles of International Law concerning Friendly Relations and Co-operation among States in accordance with the UN Charter contained in Resolution 2625 (24 October 1970) and several ‘declarations’ adopted by the General Assembly recognizing certain principles applicable to a specific matter, such as those contained in Resolution 217A (10 December 1948, establishing the Universal Declaration of Human Rights), Resolution 1514 (14 December 1960, establishing the Declaration on the Granting of Independence to Colonial Countries and Peoples) and Resolution 1962 (13 December 1963, establishing the Declaration of Legal Principles Governing the Activities of States in the Exploration and Uses of Outer Space).

2. Acts of International Organizations and other Sources of International Law edit

Resolutions of international organizations may also relate to other sources of international law. Firstly, such acts can contribute to the development or consolidation of customary rules of international law. In the Advisory Opinion concerning the Legal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965 the ICJ understood that although formally a recommendation, UNGA Resolution 1514 (XV) establishing the Declaration on the Granting of Independence to Colonial Countries and Peoples ‘has a declaratory character with regard to the right to self-determination as a customary norm’ and clarified the content and scope of the right to self-determination, representing a ‘defining moment in the consolidation of State practice on decolonization’.[46] Secondly, resolutions may also be relevant in the interpretation of international treaties and even constitute subsequent practice for the purpose of treaty interpretation.[47] In the Whaling in the Antarctic case, for instance, the ICJ considered that resolutions from the International Whaling Commission may be relevant for the interpretation of the International Convention for the Regulation of Whaling when adopted by consensus or by a unanimous vote, even not having a binding effect.[48]

3. Acts of International Organizations beyond the Concept of Legal Source of Rights and Obligations edit

The classic definition of sources of international law may be insufficient to apprehend the legal significance of acts of international organizations to international law as they can hardly be considered as an independent category of sources of international law for not being able to create autonomously rights and obligations for States. Traditionally, it is recognized that acts of international organizations usually are the result of a political compromise that does not intend to create legal obligations by itself. This understanding is shared by the practice of the ICJ, which often rejects the claim that resolutions create legal obligations for States that consent to them. For instance, in the Nicaragua case, the Court rejected the claim that a resolution of the Meeting of Consultation of Ministers for Foreign Affairs of the Organization of American States had established a legal undertaken for Nicaragua regarding its domestic policy.[49] In the case concerning the Obligation to Negotiate Access to the Pacific Ocean of 2012, the Court rejected the claim that resolutions adopted by the General Assembly of the Organization of the American States had created a legal obligation for Chile to negotiate Bolivia’s access to the Pacific Ocean, even if adopted with its consent.[50]

Nevertheless, the legal importance of resolutions of international organizations goes beyond the legal effects traditionally assigned to them. Often such acts affect the behaviour of States and other international actors even without the establishment of legally binding rules, which may be observed in the context of the role of international organizations in global governance. It is increasingly common for international organizations to adopt resolutions containing standards, practices and procedures which provide a normative framework for the exercise of public authority in several areas of international law regardless of their binding character. Such acts, which often are classified as ‘soft law’ (see section 'Soft Law' above), sometimes are preferred over traditional sources of international law for the facility in their creation and flexibility. This may be seen, for instance, in the regulatory function of the food standards issued by the Codex Alimentarius Commission, the Code of Conduct for Responsible Fisheries of the UN Food and Agriculture Organization (FAO) and the OECD Guidelines for Multinational Enterprises, all of which with significant regulatory form even without binding character.[51] Another important example concerns the role of the World Health Organisation (WHO) in global health governance, especially regarding the COVID-19 pandemic. The coordination between public and private international actors for the fight against the virus was done by the WHO not only through binding rules provided for by the International Health Regulations (2005) but also by temporary and non-binding recommendations adopted on advice of an Emergency Committee composed by experts of different fields.[52]

III. Unilateral Declarations edit

Besides soft law and acts of International Organisations, unilateral declarations are often discussed as a further candidate for a source beyond Art. 38 of the ICJ statute. The question is whether declarations states make towards other states or the international community, for example a promise to act in a certain way, may deploy legal effects. In other words, can states be legally bound by statements or announcements they made? In the Nuclear Tests case,[53] the ICJ has answered this question in the positive under certain conditions, deducing the legal bindingness from the principle of good faith, a general principle under Art. 38(1)(c) ICJ Statute. In this case, the ICJ among other things had to determine whether France was bound by its announcements in various public statements to refrain from carrying out further atmospheric nuclear tests in the South Pacific region. In order not to deduce legal effects from merely political statements, the ICJ developed three criteria:

  • The declaration must have been made by the competent authority in a framework that indicates seriousness;
  • The declaration must be sufficiently specific, and
  • it must indicate the intention to be legally bound.[54]

A specific form is not required according to the Court; this means that also oral statements can deploy legal effects. Also further unilateral acts of states can have certain legal effects, as discussed in other chapters. By way of example the protesting state under the persistent objector doctrine can avoid being legally bound by emerging customary international law (see chapter on customary international law); also recognition by states has legal effects (see the chapter on States). Under the constitutive theory, recognition of states is constitutive for statehood; international organisations only possess partial international legal personality because of the designation by states (see chapter on International Organizations).

Further Readings edit

  • Samantha Besson (2010). Theorizing the sources of international law. In The philosophy of international law (pp. 163-185). Oxford: Oxford University Press.
  • Gilbert Guillaume (2011). The use of precedent by international judges and arbitrators. Journal of International Dispute Settlement, 2(1), 5-23.
  • Christian Tams (2014). The World Court's Role in the International Law-Making Process. Available at SSRN 2406311.
  • Antonio Tzanakopoulos (2016). Domestic judicial lawmaking. In Research Handbook on the Theory and Practice of International Lawmaking (pp. 222-241). Edward Elgar Publishing.
  • Gleider Hernández (2016). International judicial lawmaking. In Research Handbook on the Theory and Practice of International Lawmaking (pp. 200-221). Edward Elgar Publishing.

Conclusion edit

  • Sources beyond Art. 38 exist, and highly relevant. International law not suited to cope with rapidly changing circumstances; this is why other, more flexible sources are highly important. In times of global governance, the decisions of international courts, resolutions of IOs and soft law are highly relevant and regulate many aspects of our lives. Importance of secondary law. Putting into question the formal distinction between law and non-law. Is it international law or not, and does it even matter? https://oxford.universitypressscholarship.com/view/10.1093/acprof:oso/9780199658589.001.0001/acprof-9780199658589-chapter-7?rskey=alOaLg&result=1
  • Debates about informal international law. Realists and New Haven school - relevance, influence of norms on behavior of states matters and not their form. However, as important as informal sources of international law might be, the distinction of law and non-law is certainly not entirely redundant. Even though international courts might take other sources into account, they rule on the basis of formal law; also countermeasures.
  • Risk to further undermine democratic legitimacy of international law? See debates in Switzerland about parliamentary approval for soft law instruments.
  • Summary I
  • Summary II

Table of Contents edit

Back to home page

Part I - History, Theory, and Methods

Part II - General International Law

Part III - Specialized Fields

Footnotes edit

  1. a b c Alain Pellet/Daniel Müller, Art. 38, in Andreas Zimmermann, Christian J. Tams, Karin Oellers-Frahm, and Christian Tomuschat, The Statute of the International Court of Justice : A Commentary (OUP 2019), para. 338.
  2. Venzke, I, How Interpretation Makes International Law: On Semantic Change and Normative Twists. Oxford: Oxford University Press 2012, 66.
  3. See on this Armin von Bogdandy and Ingo Venzke (eds), ‘Beyond Dispute: International Judicial Institutions as Lawmakers’ Special Issue (2011) 12 German Law Journal 979–1370.
  4. Charles C. Jalloh, Subsidiary means for the determination of rules of international law, International Law Commission, A/76/10, 188.
  5. Procès-verbaux [1920] 306.
  6. ICJ. Fisheries Jurisdiction (United Kingdom v Iceland) (Merits) (Judgment) [1974] ICJ Rep 53
  7. Thirlway, Hugh (2019). Sources of International Law (2nd ed.). Oxford: Oxford University Press.
  8. Sorensen, Max (1946). Les sources du droit international (in French) (1st ed.). Copenhagen: Einar Munksgaard.
  9. Jennings, Robert, ed. (2008). Oppenheim's International Law Volume 1 Peace (9th ed.). Oxford: Oxford University Press.
  10. RY Jennings, What is International Law and How Do We Tell It When We See It?' [1981] 37 Schweitzerisches Jahrbuch für lnternationales Recht  (1981) 41
  11. A Pellet, Decisions of the ICJ as Sources of International Law?, 2 Gaetano Morelli Lectures Series (2018) 7-63.
  12. GG Fitzmaurice, Some problems regarding the formal sources of international law, Symbolae Verzijl (Nijhoff 1958) 153-176.
  13. On this issue, see, among others, L Condorelli, L’autorité de la décision des juridictions internationales permanentes, in Société française pour le droit international, La Juridiction internationale (Pedone 1987) 277–313;
  14. On this topic, see FL Bordin, Reflections of customary international law: The authority of codification conventions and ilc draft articles in international law [2014] 63 International and Comparative Law 535
  15. V Lowe, A Tzanakopoulos, The Development of the Law of the Sea by the International Court of Justice, in CJ Tams, J Sloan (eds) The Development of International Law by the International Court of Justice (OUP 2013) 177.
  16. See, for instance, M Shahabuddeen, Precedent in the World Court (CUP 2010); M Forteau, Les décisions juridictionnelles comme précédent, in Société Française pour le Droit International, Le précédent en droit international (Pédone, 2016) 87-112; MBENGUE, Makane Moïse. Precedent. In: Jean d’Aspremont and Sahib Singh. Concepts for International Law. Cheltenham : E. Elgar, 2019. p. 708-718. For a more recent reading of the phenomenon, see JG Devaney, The Role of Precedent in the Jurisprudence of the International Court of Justice: A Constructive Interpretation [2022] Leiden Journal of International Law, First view, 1.
  17. Application of the Convention on the Prevention and Punishment of the Crime of Genocide (Croatia v. Serbia), Merits, Judgment of 3 February 2015, [2015] ICJ Rep., at 3, para. 54
  18. See, for instance, E De Brabandere, The Use of Precedent and External Case Law by the International Court of Justice and the International Tribunal for the Law of the Sea [2016] 15(1) The Law & Practice of International Courts and Tribunals 24; Y Lupu, E Voeten, Precedent in International Courts: A Network Analysis of Case Citations by the European Court of Human Rights [2012] 42 British Journal of Political Science 413; ITLOS, The “Grand Prince” Case (Belize v. France), Prompt Release, Judgment of 20 April 2001, para. 78; ITLOS, The M/V “Louisa” Case (Saint Vincent and the Grenadines v. Kingdom of Spain), Judgment of 28 May 2013, para. 81; United States Import Prohibition of Certain Shrimp and Shrimp Products, WTO Appellate Body Report, 12 October 1998, WT/DS58/AB/R, para. 67; Al-Adsani v United Kingdom (App no 35763/97) ECHR 21 November 2001, paras 60-61.
  19. Ahmadou Sadio Diallo (Rep. of Guinea v. Democratic Republic of Congo), Merits, Judgment, 2010 I.C.J. Rep. 639, 664, para 67.
  20. Cançado Trindade, Antônio Augusto (2019). "The Continuity of Jurisprudential Cross-Fertilization in the Case-Law of International Tribunals in their Common Mission of Realization of Justice". The Global Community Yearbook of International Law and Jurisprudence (1st ed.). Oxford: Oxford University Press. pp. pp. 247-268. {{cite book}}: |pages= has extra text (help)
  21. Giorgetti, Chiara (2015). "Cross-Fertilisation of Procedural Law Among International Courts and Tribunals: Methods and Meanings" (PDF). University of Richmond UR Scholarship Repository – via SSRN.
  22. Nollkaemper, Andre (2011). National Courts and the International Rule of Law (1st ed.). Oxford: Oxford University Press. ISBN 9780191725234.
  23. Vide for instance Filártiga v. Peña-Irala, 630 F.2d 876 (2nd Cir. 1980).
  24. A Nollkaemper, National courts and the international rule of law (OUP 2012) 255-256.
  25. ICJ, Jurisdictional Immunities of the State (Germany v. Italy: Greece intervening), Judgment of 3 February 2012, ICJ Reports 2012, p. 123.
  26. Text of the draft conclusions provisionally adopted by the Drafting Committee on first reading, 12 May 2023, UN Doc A/CN.4/L.982, p. 2, Draft Conclusion 8.
  27. ILC, Draft conclusions on identification of customary international law with commentaries, 2018, p. 29.
  28. PCIJ, Lotus (France v. Turkey), PCIJ Ser. A 10 (1927), 28.
  29. Text of the draft conclusions provisionally adopted by the Drafting Committee on first reading, 12 May 2023, UN Doc A/CN.4/L.982, p. 2.
  30. ILC, Draft conclusions on the identification of customary international law with commentaries, 2018, p. 13-14.
  31. ICJ, Arrest Warrant of 11 April 2000 (Democratic Republic of the Congo v. Belgium), Judgment of 14 February 2002, ICJ Reports 2002, pp. 23-24.
  32. M Lachs ‘Teachings and Teaching of International Law’ (1976) 151 RdC 161–252, at 212.
  33. See on the distinction between state-empowered and other categories of publicists Sandesh Sivakumaran, The Influence of Teachings of Publicists on the Development of International Law, International and Comparative Law Quarterly 66 (2017), 1-37, at 4 ff.
  34. Statute of the International Law Commission (International Law Commission [ILC]) UN Doc A/RES/174(II), Annex, Ch.I Organization of the International Law Commission, Art.2. See for a recent debate on the role and function of the ILC the symposium on Völkerrechtsblog, "The International Law Commission as an interpreter of international law?", edited by Justine Batura, Sué González Hauck & Sophie Schuberth, https://voelkerrechtsblog.org/symposium/the-role-of-the-ilc/.
  35. Even though the Draft Articles are not per se binding law, they in great parts reflect customary international law.
  36. See on this Sandesh Sivakumaran, The Influence of Teachings of Publicists on the Development of International Law, International and Comparative Law Quarterly 66 (2017), 1-37.
  37. Gleider Hernández, The Responsibility of the International Legal Academic - Situating the Grammarian Within the "Invisible College", in Jean d'Aspremont, Tarcisio Gazzini, André Nollkaemper and Wouter Werner (eds), International Law as a Profession, CUP 2017, 160-188.
  38. Anthea Roberts, Is International Law International? (Oxford: Oxford University Press 2017).
  39. Oscar Schachter, The Invisible College of International Lawyers, Northwestern University Law Review 72(2), 217-226.
  40. See for example Ndlovu-Gatsheni, Sabelo J.. (2017). The emergence and trajectories of struggles for an 'African university': The case of unfinished business of African epistemic decolonisation. Kronos, 43(1), 51-77. https://dx.doi.org/10.17159/2309-9585/2017/v43a4
  41. Statute of the United Nations Dispute Tribunal, Article 11(3). See also Effect of Awards of Compensation Made by the United Nations Administrative Tribunal (Advisory Opinion) [1954] ICJ Rep 47.
  42. S Talmon ‘The Security Council as World Legislature’ (2005) 99 AJIL 175-193.
  43. J Crawford, ‘Chance, Order, Change: The Course of International Law’ (2013) 365 Recueils des Cours de l'Académie de Droit International de la Haye 17, 312-313.
  44. Legality of the Threat or Use of Nuclear Weapons (Advisory Opinion) [1996] ICJ Rep 226, 254-255 (para 70).
  45. Military and Paramilitary Activities in and against Nicaragua (Nicaragua v United States of America) (Merits) [1986] ICJ Rep 14, 99-100 (para 188).
  46. Legal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965 (Advisory Opinion) [2019] ICJ Rep 95, 132-133 (para 150-153).
  47. M C Wood, The Interpretation of Security Council Resolutions (1998) 2 Max Planck Yearbook of United Nations Law 73-95, 91-92.
  48. Whaling in the Antarctic (Australia v Japan: New Zealand intervening) [2014] ICJ Rep 226, 248 (para 46). See also Military and Paramilitary Activities in and against Nicaragua (Nicaragua v United States of America) (Merits) [1986] ICJ Rep 14, 99-100 (para 188).
  49. Military and Paramilitary Activities in and against Nicaragua (Nicaragua v United States of America) (Merits) [1986] ICJ Rep 14, 132 (para 261).
  50. Obligation to Negotiate Access to the Pacific Ocean (Bolivia v Chile) (Merits) [2018] ICJ Rep 507, 562 (para 171).
  51. See in special the analysis of such regulations by Gefion Schuler, Jürgen Friedrich and Ravi Afonso Pereira in Armin Bogdandy, Rüdiger Wolfrum, Jochen Bernstorff, Philipp Dann and Matthias Goldmann (eds), The Exercise of Public Authority by International Institutions: Advancing International Institutional Law (Springer 2010).
  52. Armin von Bogdandy and Pedro Villarreal, ‘International Law on Pandemic Response: A First Stocktaking in Light of the Coronavirus Crisis’ in Max Planck Institute for Comparative Public Law & International Law (MPIL) Research Paper No. 2020-07. See also Mateja Steinbrück Platise, ‘The Changing Structure of Global Health Governance’ in L Vierck, P Villarreal and A Weilert (eds), The Governance of  Disease Outbreaks (Nomos 2017) 83-111.
  53. ICJ, Nuclear Tests Case (Australia v. France), Judgment of 20 December 1974, ICJ Reports 1974, p. 253. See already PCIJ, Legal Status of Eastern Greenland (Denmark v. Norway), PCIJ Ser. A/B 53 (1933), 22.
  54. ICJ, Nuclear Tests Case (Australia v. France), Judgment of 20 December 1974, ICJ Reports 1974, p. 253, paras. 42-46.