The international legal system is a composite set of norms, procedures, and legal regimes that make interaction and mutual action among components possible and bring them together in a coherent framework. At the same time, alongside the general system of international law, there exists the possibility of multiple subsystems within this systematic domain. The present article seeks to answer the question of what role informal international institutions play in the international legal system in managing international crises, particularly the Iranian nuclear crisis.

The primary objective of this research is to explain the position of informal international institutions in resolving international disputes, with emphasis on the resolution of Iran's nuclear program during the Rouhani administration. In this research, using the approach of "institutionalism," based on the findings, international institutions provide the possibility for states that have not achieved desirable outcomes in strategic interactions to improve their results by creating a new balance; however, the sustainability of this balance depends on the creation of shared behavioral expectations and the support of the theory of political regimes and great powers.

Nevertheless, in the Iranian nuclear crisis, the main role has appeared at the technical-monitoring level by the International Atomic Energy Agency (IAEA), and crisis resolution has emerged through the intervention of the International Crisis Group.