Transit Passage: The Legal Architecture That Iran Disputes and the World Depends On
The Strait of Hormuz is a strait used for international navigation overlapping with the territorial waters of Iran and Oman. Under the United Nations Convention on the Law of the Sea, such straits are subject to the right of transit passage — a legal regime that grants all ships and aircraft the right to continuous and expeditious transit, and that limits the ability of coastal states to interfere with that transit. Iran has not ratified UNCLOS. It does not accept the transit passage framework. This legal disagreement is not merely academic. It is the normative foundation on which Iran’s claimed right to close or restrict the strait rests, and the normative foundation that every other party invokes to deny Iran that right.
Iran’s position draws on a pre-UNCLOS framework of innocent passage, which gives coastal states substantially more control over transit through their territorial waters. Under innocent passage doctrine, a coastal state can require prior notification or permission for warships to enter its territorial sea, can impose routing requirements on commercial vessels, and — in the most aggressive reading — can suspend passage for security reasons. Iran has periodically invoked variations of this argument to justify naval exercises that disrupt normal shipping patterns, to assert the right to board and inspect foreign-flagged vessels, and, in the most extreme formulations, to claim the legal authority to close the strait during armed conflict with a belligerent that is receiving support from transit shipping.
The United States, and the overwhelming majority of maritime nations, reject this framework entirely. American freedom of navigation operations — naval transits conducted specifically to contest excessive maritime claims — have periodically been conducted in Gulf waters to demonstrate that the US does not accept Iranian restrictions on navigation. The operations are legal assertions, not provocations, though they are received as provocations by Tehran. They signal that any Iranian attempt to impose transit restrictions will be resisted not just militarily but in the prior legal layer that determines the legitimacy of the military response.
The Omani position is relevant because Oman does accept UNCLOS and because the southern lane of the strait runs through Omani territorial waters as well as Iranian. Oman’s adherence to transit passage doctrine means that even under the most restrictive reading of Iranian legal authority over its portion of the strait, vessels could in principle route through Omani waters where a different legal framework applies. The practical utility of this argument during a military confrontation may be limited. Its existence complicates any Iranian attempt to claim that closure is legally coherent under international law.
The 1982 UNCLOS negotiations specifically created the transit passage regime because the negotiators — including the United States — recognized that innocent passage, which had governed international straits under the 1958 Geneva Conventions, gave coastal states too much discretion over economically critical routes. Hormuz was not the only strait at issue; the Turkish Straits, the Strait of Malacca, the Strait of Gibraltar, and other critical passages were all part of the same negotiating package. The transit passage regime was the price that major naval powers paid for accepting other UNCLOS provisions on exclusive economic zones and the continental shelf — a grand bargain that Iran, which was in the middle of its revolution in 1979, was not positioned to participate in.
The legal architecture matters because it determines who can claim legitimate authority for their actions. A naval force escorting tankers through Hormuz under transit passage doctrine is enforcing an internationally recognized right. A naval force doing the same thing without that legal framework is simply exercising power. The distinction affects coalition building, international legitimacy, and the political sustainability of any extended escort or clearing operation. Iran’s refusal to accept UNCLOS is therefore not just a domestic legal position. It is a strategic choice to remain outside the normative framework that legitimizes the primary mechanism for keeping the strait open.
Rules that no one can enforce against a recalcitrant coastal state are not rules that the strait can depend on. They are arguments about what the rules should be, conducted at naval gunpoint.