How the Emerging US‑Iran Understanding on the Strait of Hormuz Raises Questions of International Maritime Law, UN Obligations and Treaty Validity

The emerging understanding between the United States and Iran regarding the reopening of the Strait of Hormuz follows a period of weeks marked by heightened military activity in the region, which has raised concerns about the stability of crucial energy transport routes. The United States has articulated a strategic objective of averting widespread economic disturbance that could arise from interruptions to the flow of petroleum and related commodities through this narrow maritime corridor. According to multiple reports, the parties are said to be moving toward a finalised arrangement that would facilitate the resumption of regular shipping, although the precise terms and conditions of such an arrangement have not been disclosed publicly. Iran, while indicating a willingness to discuss the reopening, has explicitly rejected any proposition that would require it to relinquish its uranium program or to guarantee an unconditional and permanent opening of the strait without reservations. The lack of clarity surrounding the final content of the anticipated agreement leaves analysts uncertain about how the parties intend to balance the competing demands of regional security, commercial imperatives and sovereign policy choices. Should the understanding be formalised, the reopening of the strait would likely restore a critical artery for global oil markets, thereby mitigating price volatility and reinforcing the reliability of supply chains that depend upon uninterrupted maritime transit. Conversely, any failure to secure concrete assurances regarding the conditions under which the strait will remain open could perpetuate the risk of future disruptions and maintain an atmosphere of strategic uncertainty in the Persian Gulf region.

One question is whether the principle of transit passage under customary international law obliges Iran to keep the Strait of Hormuz open for all vessels despite the reported diplomatic negotiations. The answer may depend on the fact that, although Iran has not ratified the United Nations Convention on the Law of the Sea, the norms governing international straits have attained the status of customary law binding on all states, including non‑parties. Thus, a unilateral closure of the strait could be deemed unlawful unless justified by a valid exception such as self‑defence, which would itself require a proportionality assessment under international legal standards. A court or tribunal reviewing any alleged breach would likely examine whether the alleged closure was proportionate to an imminent threat and whether less restrictive measures were available to achieve the stated security objective.

Another pertinent issue is whether existing United Nations Security Council resolutions concerning Iran’s nuclear programme impose constraints on any agreement that seeks to alter the operational status of the Strait of Hormuz. The answer may depend on the operative clauses of those resolutions, which typically require member states to prevent the supply of nuclear‑related materials to Iran while also calling for the maintenance of safe and secure navigation in international waters. If the emerging understanding entails the removal of sanctions that affect maritime traffic, the parties must ensure that such measures do not contravene the binding provisions of the resolutions, lest they expose themselves to allegations of violation of Chapter VII obligations. A judicial or diplomatic review could therefore focus on whether the contemplated terms are compatible with the Council’s mandate to prevent proliferation while preserving the principle of freedom of navigation.

A further question is whether the reported bilateral understanding could rise to the status of a treaty under international law, thereby acquiring the capacity to modify the parties’ respective obligations under customary or treaty law. The answer may depend on the presence of the essential elements of consent, intent to create legal obligations and a written instrument, none of which have been publicly confirmed, leaving the legal nature of the arrangement uncertain. Even if the understanding were to be characterised as a treaty, it would not automatically extinguish Iran’s customary duty to allow transit passage, unless the treaty explicitly and lawfully modifies that duty with the consent of the international community. Consequently, any legal challenge to the arrangement would likely scrutinise whether the treaty, assuming it exists, complies with the principle of pacta sunt servanda and respects the hierarchy of international obligations.

An additional legal dimension concerns the United States’ desire to prevent global economic disruption, which may involve the adjustment or lifting of secondary sanctions that currently restrict entities dealing with Iranian shipping. The answer may depend on the statutory authority under which the United States imposes such sanctions, typically derived from domestic legislation and executive orders, and whether those authorities permit targeted relief contingent upon the successful reopening of the strait. If sanctions were to be eased, the United States would need to ensure that the relief measures are consistent with any binding United Nations sanctions, thereby avoiding a conflict between domestic sanction regimes and international obligations. A legal assessment would also consider whether the prospective sanction adjustments respect principles of proportionality and non‑discrimination, which are recognised in both domestic and international law as safeguards against arbitrary restriction of trade.

In sum, the emerging US‑Iran understanding on the Strait of Hormuz raises intricate legal questions that intersect customary maritime law, United Nations resolutions, potential treaty formation and the complex architecture of sanctions regimes. A definitive legal resolution will require clarity on the precise terms of the agreement, an assessment of its compatibility with established international obligations and possibly judicial or arbitral adjudication to reconcile any conflicting duties. Until such clarity emerges, the legal community must remain attentive to how the evolving diplomatic narrative may be shaped by, and in turn shape, the normative frameworks governing navigation, non‑proliferation and international trade.