Introduction

In every legal system, the question of who is responsible for violations of established laws and regulations is inseparable from the system in that it serves as a guarantee for enforcing the law. Concerning the international responsibility, the debate centers on how and under what criteria the acts of private persons can be attributed to a state. The core issue is the international responsibility of states for the wrongful acts of private persons under their jurisdiction that affect the international arena. The main challenge lies in establishing the criteria for attributing the acts of private persons to states. In this respect, it is essential to examine the exercise of due diligence and the failure to observe it by states. The current study generally aimed to analyze the concept of due diligence within international law, focusing on its implications for state responsibility toward private persons’ acts. The analysis specifically examined due diligence in the context of the law of the sea, where private fleets constitute key actors. In such cases, attributing wrongful acts to the flag state becomes a critical concern. The research question is: What is the role of states’ failure to exercise due diligence regarding the conduct of private actors under the international law of the sea?

Literature Review

During the 19th and 20th centuries, the doctrine of due diligence attracted scholarly attention, especially regarding the protection of foreigners within a state’s territory. In English-language scholarship, this theme has been explored extensively. There are also a few Persian-language studies on the concept of due diligence. For instance, in the article “The Concept and Nature of ‘Due Diligence’ in International Law,” Hosseini and Rahaee (2024) examined the topic in the context of international human rights law. Moreover, the article “Understanding the Concept and Status of ‘Due Diligence’ in International Investment Law” (Hosseini & Habibi-Mojande, 2024) emphasized the role of due diligence in the investment law. The current study, however, deals with a different issue, namely, state responsibility for the actions of private vessels that fly its flag.

Materials and Methods

The research adopted a descriptive–analytical method. The data was collected from library sources and various documents.

Results and Discussion

Given the growing involvement of the private sector in areas traditionally dominated by the state, it is increasingly important to scrutinize the scope of states’ international responsibility for their actions. This issue is especially salient with respect to the law of the sea. Examining a range of doctrinal opinions, the analysis revealed that the concept of due diligence plays a crucial role in determining whether states bear international responsibility for the acts of private actors.
The concept of due diligence lacks a single, universally accepted definition in international law; instead, the requirements for exercising due diligence vary according to the specific context. However, according to the established practices and doctrinal opinions, the concept has several essential elements in international law, including the degree of risk predictability, the potential risks associated with various actions, and the exertion of maximum effort to mitigate those risks.
In addition, due diligence is a pivotal principle widely recognized by most doctrines on state responsibility under the law of the sea. This is particularly underscored by the 2015 advisory opinion of the International Tribunal for the Law of the Sea, which holds that a state’s international responsibility for the acts of private persons, especially fishing vessels, hinges on whether due diligence was exercised or not.

Conclusion

The current inquiry focused on state responsibility for the acts of private vessels that fly its flag, examining the extent to which a state is obligated—under the principle of due diligence—to meet its obligations under the law of the sea. According to the results, states are responsible for the unlawful acts of fishing vessels if they fail to exercise due diligence.