Is Iran's persistent-objector claim to Hormuz transit fees valid?

Iran’s proposed Strait of Hormuz fee system turns on a narrower question than whether a coastal state may dislike military traffic near its coast. The hard question is whether Iran has escaped the transit-passage rule strongly enough to charge vessels for using the strait between Iran and Oman. Put in the language of international maritime law, the dispute depends on whether Iran can make a serious persistent-objector claim against a customary rule that many states treat as already binding.

The current proposal-and-rejection sequence is already covered in Why Iran's Hormuz Corridor Rejection Has Legal Grounding. The point here is not to retell the crisis. It is to test the legal hinge Iran would need if a “voluntary” passage fee were challenged: that UNCLOS transit passage does not bind Iran either as treaty law or as customary international law.

The rule Iran must avoid

UNCLOS Part III applies to straits used for international navigation between one part of the high seas or an exclusive economic zone and another. Articles 37 to 44 establish transit passage, require that it not be impeded, and impose duties on strait states not to hamper passage or suspend it through such straits.[1] For a chokepoint like Hormuz, that is the legal architecture Iran must get around before a fee for passage alone can look defensible.

Iran has an immediate treaty answer: it signed UNCLOS in 1982 but has not ratified it. Signature is not ratification, and Iran is not bound by UNCLOS as a party in the ordinary way. That point matters. It does not, however, answer the customary-law question. A non-party can still be bound by a rule that has become customary international law, unless it preserved a valid persistent objection before the rule crystallized.

The persistent-objector doctrine is not a general license to opt out after a rule becomes inconvenient. The objection must be timely, clear, and consistent while the customary rule is forming. Chatham House’s April 2026 treatment of Hormuz frames the central dispute this way: transit passage is widely treated as customary, but the precise crystallization point and the effect of particular non-party positions remain contested rather than judicially settled.[2]

Iran’s best argument starts in 1982

The strongest version of Iran’s position does not begin with recent threats, boarding operations, or a fee schedule. It begins in 1982, when UNCLOS opened for signature and Iran signed with an interpretative declaration. Mohammad Yousef’s minority view gives that timing real legal weight: if transit passage had not yet crystallized as custom in 1982, Iran can argue that it objected early enough to preserve its position against later customary consolidation.[3]

That is not a frivolous argument. UNCLOS was a negotiated package, and Part III’s transit-passage regime was one of the political bargains that made the convention acceptable to maritime powers and strait states. If a state declared from the outset that Part III did not bind non-parties, it can plausibly say it did not sleep on its rights while a new rule silently hardened around it.

But the content of the objection matters as much as its date. Iran’s declaration was aimed at the application of UNCLOS treaty provisions to non-parties. That is a different proposition from saying: “Iran objects to the emergence of a customary international-law rule of transit passage in straits used for international navigation.” The first resists treaty extension. The second resists custom. Persistent objection needs the second kind of clarity, or at least conduct that unmistakably performs it.

This distinction is where much of the argument loses force. A state may be correct that a treaty provision does not bind it as treaty law and still be bound by a substantively similar customary rule. Non-ratification keeps a state outside the convention’s consent-based machinery. It does not, by itself, immunize the state from rules that have become customary through general practice accepted as law.

The crystallization problem cuts both ways

The timing problem cannot be solved by assertion. If transit passage was already customary before Iran’s 1982 declaration, the declaration came too late. If the rule crystallized only through UNCLOS adoption and subsequent state practice, Iran’s timing looks better. If it remains not fully customary, Iran’s case improves still further. The difficulty is that no international court has given a definitive ruling fixing the crystallization date for transit passage in the Strait of Hormuz.

That uncertainty is why institutional and scholarly characterizations should not be treated as if they were judgments. Chatham House presents the mainstream view that transit passage through Hormuz is strongly supported as customary law, but the analysis remains an expert assessment of legal materials, not a binding adjudication.[2] Yousef’s contrary emphasis on Iran’s declared position and later assertions is therefore not answered simply by counting how many writers disagree with it.[3]

Still, the burden on Iran is demanding. Persistent objection is an exception to a rule claimed against the international community. The objecting state must show more than discomfort with a treaty package. It must show a legal posture maintained with enough consistency that other states were on notice that the objector refused the customary rule itself.

Iran’s 1982 declaration helps on timing but is less helpful on category. Later conduct and statements may help on consistency, but they cannot easily repair an initial objection framed as a treaty reservation-style position rather than a custom objection. That mismatch is not semantic. It decides whether Iran preserved an exception to custom or merely explained why it did not accept UNCLOS Part III as conventional law.

The non-party problem is not only Iran’s

Iran also has to confront a more awkward comparator: the United States. The United States is not a party to UNCLOS either, yet it has long treated the convention’s navigation and overflight rules, including transit passage, as reflecting customary international law. The U.S. Navy’s 2022 Commander’s Handbook states that the United States considers the navigational provisions of UNCLOS reflective of customary international law, including transit passage through international straits.[4]

That position matters precisely because the United States is a non-party. If all non-parties behaved like Iran, the case for excluding non-parties from transit passage might have a cleaner shape. But a major non-party that asserts and operationalizes transit passage as custom makes it harder for Iran to portray non-ratification as a general exemption from Part III norms.

U.S. freedom-of-navigation practice reinforces the point. It is not a court judgment, and it is not neutral evidence in the way a judgment would be. But state practice does not become irrelevant because it is strategic. Practice accompanied by an asserted legal right is exactly the kind of material lawyers examine when asking whether a customary rule exists and whether other states have accepted or resisted it.

The Lawfare analysis of the U.S.-Iran maritime posture describes the United States’ legal position against restrictions on shipping through Hormuz in terms that track this broader commitment to navigation rights.[5] Again, that does not end the matter. It does, however, weaken the move from “Iran did not ratify UNCLOS” to “Iran is outside the transit-passage regime.” Another non-party’s practice points the other way.

A fee is harder to defend than a security measure

Even if Iran succeeded in avoiding UNCLOS transit passage as custom, the fee system would not automatically become lawful. That is the part often lost when the argument is presented as a binary choice between UNCLOS and Iranian discretion. Iran has ratified the 1958 Geneva Convention framework, and the fallback is therefore not a legal vacuum.

The older regime is built around innocent passage rather than UNCLOS transit passage. Innocent passage gives coastal states more room than transit passage, especially where security is concerned. But more room is not the same thing as a tolling power. The Eno Center’s analysis of Hormuz tolling separates charges connected to actual services from charges imposed merely for passage; that distinction is central to whether a “voluntary” fee can survive legal scrutiny.[6]

A charge for pilotage, rescue, port services, environmental response, or another identifiable service occupies a different legal category from a charge levied because a vessel crossed a strait. A passage fee is especially vulnerable where the ship neither requests nor receives a service proportionate to the charge. Calling the system voluntary does not cure the defect if the surrounding facts show that payment is extracted under threat of delay, inspection, diversion, or interdiction.

Regional legal commentary reaches a similar practical point: access to Hormuz cannot be reduced to a coastal-state revenue claim merely because the waterway is physically narrow and politically exposed.[7] Control over a chokepoint creates leverage. It does not by itself create a fee entitlement.

Institutional rejection helps, but does not decide custom

Security Council and IMO reactions to Iranian toll claims are useful, but they need to be kept in the right legal box. The research record identifies UNSC Resolution 2817 in 2026 and IMO council statements as explicit rejections of Iran’s position on tolls. Those materials are evidence of international legal opposition and opinio juris. They are not, without more, a judicial determination that transit passage is customary law or that Iran failed as a persistent objector.

That limitation matters. A Security Council resolution adopted in a peace-and-security setting may condemn conduct, demand restraint, or authorize consequences without settling the underlying customary-law pedigree of every rule it invokes. IMO statements likewise carry institutional weight in maritime governance, but they are not judgments between parties. The better use of these materials is cumulative: they show that Iran’s fee theory faces broad international resistance, not that the doctrinal question has disappeared.

Practical coercion is a separate question

A weak legal claim can still impose real costs. Ships can be delayed, insurers can reprice risk, charterers can reroute, and owners can pay to avoid confrontation. That practical dimension is better treated separately from the legal merits; the operational limits of law in the tanker crisis are addressed in How international law fails in the Strait of Hormuz tanker crisis.

That separation is not academic tidiness. It prevents two mistakes. One is assuming that illegality prevents enforcement. The other is assuming that successful coercion validates the legal theory. A fee system can become commercially hard to avoid while remaining legally exposed.

The likely legal result

Iran’s best argument is the early one: it signed UNCLOS in 1982 with a declaration, at a time when it can argue transit passage had not yet crystallized as customary law. That argument deserves to be taken seriously because persistent objection is timing-sensitive, and the crystallization of transit passage has not been conclusively fixed by an international court.

The argument remains structurally weak. Signature is not ratification, but it is also not a custom objection. Iran’s declaration targeted the treaty effect of Part III on non-parties, not necessarily the emergence of a customary transit-passage rule. Subsequent Iranian assertions have to carry the weight of converting that treaty-position into a persistent objection to custom. Against that, other non-party practice, especially the United States’ long-running customary-law position and freedom-of-navigation practice, cuts sharply against any simple non-party exemption.

The fallback does not save the fee. If Iran is not bound by UNCLOS transit passage, it still faces the 1958 innocent-passage framework and the broader distinction between charges for actual services and charges for passage alone. A Hormuz passage fee dressed as voluntary payment remains difficult to defend if the legal substance is a toll for crossing an international strait.

Iran may be able to impose costs in practice through coercion, inspection, delay, or interdiction. Its persistent-objector claim, however, is unlikely to survive cleanly in an international forum. That leaves the fee system practically threatening but legally exposed, rather than validated by Iran’s non-ratification of UNCLOS.

References

1. UNCLOS Part III, Articles 37–44, United Nations
2. Strait of Hormuz shipping and law, Chatham House, April 2026
3. Does Iran Possess the Right to Close the Strait of Hormuz under International Law?, International Law Blog, April 2026
4. NWP 1-14M 2022, U.S. Navy, 2022
5. The U.S.-Iran MOU and the Future of Maritime Shipping Through the Strait of Hormuz, Lawfare
6. The Legal Question of Tolling Hormuz, Eno Center for Transportation
7. Access to the Straits of Hormuz, Transit Fees and the International Law of the Sea, RSDI