The principle of the permanent sovereignty of states over natural resources, including water resources, has become one of the foundations of international law since the 1950s, and has been emphasized in numerous international instruments, such as Article 2(1) of the Charter of Economic Rights and Duties of States (1974).

In its classical interpretation, this principle pertains to the absolute and exclusive authority of states to exploit natural resources within their territorial domain, such that no foreign state may claim precedence or intervene in this exploitation. However, in cases where unilateral exploitation of shared water resources results in the violation of the principles of sustainable development, causes transboundary harm, or threatens international peace and security, the right of sovereignty is accordingly restricted, and the obligations of states are elevated beyond customary duties to the level of peremptory norms or erga omnes obligations.

This article, focusing on the conflict between the exercise of upstream states' sovereignty over water resources and the necessity of observing the principle of sustainable development in relation to downstream states, seeks to revisit conceptual developments in international water law. Within this framework, international instruments and judicial precedents of the International Court of Justice are examined.

The article further analyzes the concept of "water security" as an emerging doctrine, along with notions such as "water aggression" and "anticipatory self-defense." In the final section, Iran's recent water and legal challenges with its neighbors over the Helmand and Harirud rivers and Turkey's Anatolia Project, are critically assessed.