The 77th Session of the ILC through the Eyes of Research Assistants to a Commission Member. Part 4. Due diligence in international law

The International Law Commission (ILC) addresses some of the most topical issues in international law. Its work is closely followed by many international lawyers. The ILC’s current and long-term programmes of work include issues that are also within the research agenda of the International and Comparative Law Research Center. At various times, the ICLRC has worked on some specific issues that are currently under consideration by the Commission, analyzing relevant State practice, and, at the request of Commission special rapporteurs on particular topics, compiling Russian-language materials on State practice and doctrine.

Since 2024, ICLRC researchers have also participated in ILC sessions as research assistants to the ILC member Mr. Evgeny Zagaynov (Russian Federation). In 2025, Aleksei Petrenko, ICLRC Senior Researcher in Public International Law, attended the meetings in Geneva in that capacity. Aleksei prepared an overview (in Russian) describing the Commission’s functions and role, the status of its work on various topics, and his personal impressions of the ILC’s 76th session.

From April 27 to June 5 and from June 29 to July 30, 2026, the Commission held its 77th session at the United Nations Office at Geneva. Egor Fedorov, Head of Research Projects (Law of the Sea), and Anastasiia Santalova, and Andrey Buyankin, Associate Researchers in Public International Law, participated as research assistants to Mr. Evgeny Zagaynov and share their impressions of the convened work.

In a series of publications, Egor, Anastasiia, and Andrey discuss the principal issues and the course of the debates on the topics that they had an opportunity to work on.

Andrey Buyankin

The topic “Due diligence in international law” was included in the Commission’s programme of work at its previous, seventy-sixth session in 2025. At the same session, Ms. Penelope Ridings of New Zealand was appointed Special Rapporteur (SR). This year, the Commission had before it the first report of the Special Rapporteur, which addressed preliminary issues: identifying the main directions of, and approaches to, future work, including the range of issues to be studied, methodology, and sources. The report contained a historical overview of the application of the concept of due diligence in various areas of international law. At the end of the report, questions were put forward for the Commission’s further work.

Determining the place and role of due diligence in international law is of interest to the Commission, since in recent years this concept has been increasingly used in various areas of international law. For example, the International Court of Justice recently clarified the content of due diligence in the context of the obligations of States in respect of climate change in its advisory opinion (for more details, see the Center’s publication).

At the session itself, attention focused mainly on several interrelated issues:

• the scope of the topic,

• the legal nature of due diligence,

• the relationship between due diligence and certain principles in international law,

• the relationship between due diligence and the rules on the international responsibility of States,

• the characterization of due diligence as an obligation of result or an obligation of conduct,

• the final form of the outcome of the Commission’s work,

• future work on the topic.

Scope of the topic

The first aspect, and the one that would in many ways determine the future course of the work, was the scope of the topic: before going any further, the Commission needed to determine precisely which phenomena are covered by this notion.

This proved to be no easy task, however, since the very existence of due diligence as a standard or rule of general international law, as well as its legal nature, are matters of disagreement. Without a clear understanding of what “due diligence” is, it is difficult to determine the scope of a topic bearing that title.

The report indicates that “due diligence” is generally understood to refer to two main phenomena:

1. a stand-alone obligation of a State to prevent harm to the interests of other States resulting from activities carried out in its territory or under its control or jurisdiction. This obligation was articulated by the International Court of Justice in the Corfu Channel case, in which the Court referred to “every State’s obligation not to allow knowingly its territory to be used for acts contrary to the rights of other States”. This obligation was subsequently widely developed and disseminated in the field of environmental protection;
   
   
2. a legal construct (standard) that may potentially apply in conjunction with other obligations and supplement their content, thereby affecting their performance. In particular, such a standard requires States to take the necessary and available measures to implement an obligation, as well as to exercise due control over the activities of private persons. Such a standard can be found in human rights law (the obligation to prevent violence against private individuals), international investment law (the full protection and security standard), diplomatic law (the obligation to prevent attacks on an embassy by private persons), the multilateral climate change regime (the standard of due diligence in the preparation and implementation of nationally determined contributions), and so forth.

Evgeny Zagaynov (Russian Federation) at the meeting on 3 July 2026

“The standard of due diligence has a general substantive framework, but acquires its final form only in context, when applied to primary obligations, and only in conjunction with other obligations does it produce a specific legal effect. Like a lens, the standard of due diligence is superimposed on obligations and gives them a certain tint or appearance, thereby determining and/or specifying their performance. A lens has certain characteristics in itself, but produces no image unless it is applied to something.” 

In examining due diligence in its second meaning, the Commission faced an additional question: what is a “standard” in international law, and does it have independent normative content? The discussions in the ILC showed that no common approach to understanding this notion has yet emerged.

As Mr. Evgeny Zagaynov emphasized, what is at issue is a construct that has no independent, fixed normative content of its own, that is, in isolation from a specific rule of law. In his view, this construct is applied to existing international legal obligations and determines their performance. He pointed out that the International Court of Justice, in its advisory opinion on the obligations of States in respect of climate change, uses different formulations — the “standard of due diligence” and the “obligation to act with due diligence” — although the request for the advisory opinion itself uses the term “duty of due diligence”. The International Court of Justice does not formulate a general definition of due diligence, nor does it regard the criteria it developed with respect to the efforts of States to combat climate change as exhaustive or as constituting a specifically defined rule of conduct. At the same time, other members of the Commission were more inclined to see independent normative content in the standard. Mr. George Rodrigo Bandeira Galindo (Brazil) stressed the need for caution so as not to confuse due diligence as a standard of conduct with non-binding standards. In summing up, the SR endorsed the position expressed by Mr. Mathias Forteau (France), Mr. Olufemi Elias (Nigeria), and Mr. Alioune Sall (Senegal), namely that the very use of the term “standard” should not deprive due diligence of its binding character.

The distinction between the two meanings of due diligence (as a stand-alone obligation and as a standard) is highly significant for determining the scope of the topic and the extent of the Commission’s future work. In her first report, Ms. Penelope Ridings proposed to examine both phenomena; however, not all members of the Commission supported this approach. Some expressed doubts as to whether both categories needed to be developed. For instance, Mr. Evgeny Zagaynov stressed that due diligence as a stand-alone obligation to prevent harm had already been considered by the Commission in the course of its work on the draft articles on prevention of transboundary harm from hazardous activities. The idea of focusing on the study of due diligence as a standard was also supported by Mr. Dapo Akande (United Kingdom) and Mr. Mārtiņš Paparinskis (Latvia).

However, the majority of the members of the Commission agreed with the SR’s proposal to examine due diligence in both of its meanings. In summing up, Ms. Ridings pointed out that, during the meetings of the Sixth Committee of the UN General Assembly, a number of States had expressed the wish that both aspects of due diligence be studied. In her view, the written statements submitted by States in the advisory proceedings concerning climate change, as well as their national positions on the application of international law to cyberspace, demonstrate increasingly explicit support for due diligence as a stand-alone obligation.

In focus — due diligence as a phenomenon of international law

Both in the report itself and in her summing-up, the SR emphasized that due diligence in domestic law (for example, due diligence that parties to a contract are required to exercise towards each other) is not, as such, the subject of study under the present topic. Nevertheless, domestic law materials may be relevant for identifying rules of international law. Thus, Mr. Bimal N. Patel (India) cited a number of historical examples of due diligence from Indian law, noting that the underlying idea — that power entails a duty to exercise vigilance and responsibility — is neither new nor the property of any single civilization. He further noted that studying due diligence in international law from the perspective of national legislation and case law is crucial, since the harm suffered by developing countries is often the result not of direct wrongful acts, but of the failure of States and corporations to exercise due diligence.

Terminological difficulties

A few words should also be said about the term “due diligence” itself. The English title of the topic uses the expression “due diligence”. At the same time, other terms are also used to designate obligations and/or standards of similar content and meaning: “due regard”, “due care”.

Terminological diversity also exists in Russian: one may encounter both «должная осмотрительность» (literally, “due circumspection”) and «должная заботливость» (“due care”). It may be preferable to refer to due diligence as a standard of conduct as «должное усердие», since this term more accurately reflects the expectation that the obligated party will apply its own efforts to achieve a particular objective, rather than merely exercise attentiveness towards, and control over, the actions of others. It is not the Commission’s task to determine the appropriate term in Russian; however, as the work progresses and the content of the notion under study becomes clearer, it will be easier to select the most accurate Russian equivalent for use in the Commission’s documents. Even so, established usage must be taken into account when introducing new terms.

In the context of terminology, it should also be noted that the SR considered it necessary, in the course of further work, to identify and examine so-called “trigger words”, that is, terms and expressions presumably used in formulating international legal obligations to signal due diligence (for example, “ensure”, “prevent”, “protect” or “take all necessary measures”).

Obligations of States and international organizations

In her first report, Ms. Penelope Ridings proposed to examine only the due diligence obligations of States. However, during the discussions at the Commission’s plenary meetings, some members stressed the importance of also studying the practice of international organizations. As Mr. Mathias Forteau pointed out, a number of States have transferred part of their competences to the supranational level, thereby shifting the relevant practice to the level of international organizations. Moreover, the practice of international organizations may reflect the manner in which obligations are implemented by States.

Concluding the discussion, the SR stressed the need to distinguish between two questions: which obligations are covered by the topic, and on what practice the Commission’s work will be based. In her view, extending the scope of the topic to the obligations of international organizations would be undesirable. The same considerations would apply to the obligations of private persons.

Legal nature and source of due diligence

Determining the legal nature and source of due diligence as a stand-alone obligation to prevent harm posed no difficulty during the session. As reflected in the first report, this obligation is customary in nature.

However, when due diligence as a standard of conduct was discussed, the question of its source became rather acute. Broadly speaking, several options can be identified: 1) international custom; 2) a general principle of law formed within the international legal system, or 3) derived from national legal systems; 4) treaties (although this option implies that there may be no general standard at all, given the autonomy and specificity of treaty regimes).

In the context of the last option, Mr. Paparinskis pointed out that the standard of due diligence may be a way of formulating an obligation rather than a customary rule or a general principle. In essence, in his understanding, due diligence comes close to a treaty-drafting technique not enshrined in any particular source.

In response, the SR observed that she was inclined towards the position of those colleagues, such as Mr. Rolf Einar Fife (Norway), who considered due diligence to be “an integral part of the substance of primary obligations”. She also noted that due diligence obligations are not only enshrined in treaties but also exist under customary international law, while their content may be determined by specific formulations agreed upon by States. Whatever the source of due diligence as a standard of conduct, in the SR’s view, due diligence is not merely a treaty-drafting technique.

For his part, Mr. Patel cited a number of examples of due diligence obligations from the legal history of India (see above). In response, the SR noted that this led her to think that due diligence could be a general principle of law derived from national legal systems.

Several important ideas were expressed regarding the possibility of considering due diligence as a general principle of law formed within the international legal system. Mr. Claudio Grossman Guiloff (Chile) observed that, in order to recognize due diligence as a general principle of law, it is not necessary to establish the existence of the practice and opinio juris required for custom. Mr. Ahmed Amin Fathalla (Egypt) spoke along similar lines. In his view, due diligence is at present best characterized as a general principle of law. For due diligence to be recognized as international custom, both the requisite practice and opinio juris may be lacking. However, he noted that due diligence may become international custom in the future.

Bearing in mind the Commission’s ongoing work on this issue, Mr. Zagaynov stressed that the category of general principles of law formed within the international legal system cannot serve as a “shortcut” for establishing rules by circumventing the requirements established for international custom. Moreover, it is necessary to analyze whether the Commission is dealing with an already crystallized principle of law, or whether it is premature to speak of a settled, uniform normative content of due diligence.

In addition, some members of the Commission noted that due diligence may simultaneously constitute both international custom and a general principle of law. Many stressed that determining its legal nature at this stage is premature and that this question is, on the whole, of secondary importance. The question of the source in which due diligence as a standard of conduct is enshrined, and of its legal nature, will be considered in greater detail in subsequent reports on the topic.

Relationship between due diligence and certain principles in international law

In the course of the discussion, parallels were drawn with various principles of a similar nature, in particular the principles of good faith, proportionality, and common but differentiated responsibilities.

The members of the Commission did not express any position on the relationship between due diligence and good faith, merely pointing to the importance of examining that relationship in the course of further work. At the same time, Mr. Keun-Gwan Lee (Republic of Korea) cautioned against equating good faith with due diligence.

Mr. Fife noted that the principle of proportionality applies differently depending on the area of international law. Similarly, due diligence may be an objective standard, the application of which depends on the specific circumstances.

Some members of the Commission drew attention to the relationship between the standard of due diligence and the principle of common but differentiated responsibilities, and stressed the importance of taking into account the capabilities of States when determining the content of this standard.

Relationship between due diligence and the “secondary” rules of international law on responsibility

In the course of the Commission’s work, the question arose whether due diligence belongs to the primary rules of international law, which directly govern the conduct of States, or to the secondary rules on responsibility, which govern the consequences of a breach of primary rules by States. The question of the link between due diligence and secondary rules stems in part from the history of the work on the topic of responsibility of States for internationally wrongful acts. At that time, it was suggested that due diligence could serve as a basis for establishing the responsibility of States in cases where specific conduct cannot, for one reason or another, be attributed to a particular State. For example, where violence is used against an individual by persons not controlled by the State, the latter may bear responsibility for a breach of its due diligence obligation to ensure the safety of that individual. As Special Rapporteur F. V. García-Amador (Cuba) pointed out in the course of the work on the topic of responsibility of States for internationally wrongful acts, in such a case the issue is not the imputation to the State of the acts that caused the injury, but the non-performance of a duty, which is often difficult to define.

During the session, a number of members (for example, Mr. Bimal N. Patel, Mr. Hong Thao Nguyen (Viet Nam), and others) argued that the relationship between due diligence and the rules on State responsibility should be examined further. Mr. Fife, Mr. Forteau, and other members of the Commission urged caution in this regard. Thus, Mr. George Galindo noted the difficulty of distinguishing between primary and secondary rules. Mr. Elias stressed that due diligence concerns the content and performance of substantive obligations, but that failure to meet the criteria established by the standard of due diligence may entail responsibility. As to the characterization of due diligence as a primary or secondary rule, Mr. Evgeny Zagaynov stressed that, in his view, due diligence relates to the primary rules, since it is directly linked to determining the content of a particular rule of conduct. At the same time, he pointed out the importance of considering whether due diligence, or some part of it, might fall within the sphere of secondary rules.

In summing up, the SR indicated that the question of the relationship between due diligence and the secondary rules on State responsibility could not be avoided, and undertook to address it in subsequent reports on the topic.

Characterization of due diligence as an obligation of result or an obligation of conduct

Also on the agenda was the question of whether a due diligence obligation is an obligation of result or an obligation of conduct. The report does not propose an answer to this question at the current stage of the work.

This issue elicited mixed responses in the Commission. Thus, Mr. Paparinskis suggested examining whether the term “due diligence” is simply a synonym for the notion of an “obligation of conduct”. Mr. Xinmin Ma (China) noted that not every obligation of conduct is a due diligence obligation, and that this may depend on the intentions of the States involved in formulating the rule. Mr. Galindo took the view that due diligence is not an obligation of conduct. A number of members (for example, Mr. Nguyen and Mr. Elias) pointed out that due diligence may interact with obligations of result, for example, obligations to adopt particular legislation. Mr. Grossman suggested that the Commission further clarify the difference between obligations of conduct and obligations of result.

The Special Rapporteur proposed to continue examining how due diligence relates to the division of obligations into obligations of result and obligations of conduct. This would make it possible to provide practical guidance to States on how to determine the nature of obligations requiring due diligence and what consequences their assumption entails.

Final form of the outcome of the Commission’s work

The report indicates that the preferred form for the outcome of the Commission’s work could be draft principles. During the discussions, a number of members of the Commission expressed support for this form.

At the same time, Ms. Vilawan Mangklatanakul (Thailand) suggested leaving the question open; Ms. Nilüfer Oral (Türkiye) preferred draft conclusions; and Mr. Giuseppe Nesi (Italy) preferred draft guidelines. Mr. Paparinskis also allowed for the possibility that consideration of each of the “types” of due diligence might lead to different outcomes.

Summing up the discussion, the SR reaffirmed her position that draft principles could be considered the most appropriate outcome of the work. At the same time, she noted that it was not necessary to take a final decision on the form of the outcome at this stage. If necessary, the Commission would be able to return to this question at its next session.

Future work on the topic

The report indicated that a second report would be submitted to the Commission at its next, seventy-eighth session, containing draft principles concerning the scope of the topic and the use of terms, and setting out the circumstances in which the obligation to exercise due diligence arises. That report would also consider such elements as variability, knowledge, risk, and severity of harm, the capacity to control the activity giving rise to the risk, the standard of reasonableness, and other relevant factors taken into account in assessing whether a State has met the standard of due diligence.

Summing up the discussion, the SR confirmed her intention to adhere to the original plan of work. At the same time, she took particular note of Mr. Forteau’s suggestion to consider due diligence first as a standard of conduct and only then to proceed to its analysis as a stand-alone obligation. In the light of the “remarkable convergence” within the Commission regarding the understanding of due diligence as a standard of conduct, the Special Rapporteur considered it appropriate to include in the second report draft principles devoted specifically to this aspect.