UN Convention on the Law of the Sea

The United Nations Convention on the Law of the Sea, adopted in 1982 and entering force in 1994, is the foundational treaty governing maritime rights. It codifies transit passage through international straits, exclusive economic zones, continental shelf rights, and freedom of navigation. 168 state parties have ratified it; the United States has not, though it treats most provisions as customary international law.

The 2026 Iran conflict has placed UNCLOS under the most severe structural stress since its entry into force. Iran demands sovereignty over the Strait of Hormuz as a peace condition, a claim that directly contradicts UNCLOS's guarantee of transit passage through international straits used for international navigation. The IRGC's toll system, charging vessels up to $2 million per VLCC transit in yuan or stablecoins, violates the convention's core principle that straits connecting high seas cannot be subject to unilateral fees. The EU formally rejected Trump's suggestion of a US-Iran joint toll-collection venture, noting it would breach UNCLOS customary law. The 51-nation Paris mission's legal spine rests on UNCLOS transit-passage doctrine, and IMO Secretary-General Arsenio Dominguez invoked UNCLOS in his 17 April statement covering 20,000 stranded seafarers.

The Iran-Oman bilateral transit protocol confirmed by IRNA on 27 April introduces a novel UNCLOS-compliant workaround: because Oman's territorial waters cover the southern half of the 33-kilometre strait, a toll administered through Oman sits within a UNCLOS-party state's sovereign jurisdiction rather than as a unilateral imposition on an international strait. Whether this manoeuvre is compatible with UNCLOS's transit-passage protections will depend on whether the protocol is structured as a fee for services (potentially permissible) or a toll on transit passage (prohibited).

Beyond Hormuz, UNCLOS governs the legal framework for maritime operations in the Black Sea (Russia-Ukraine), South China Sea (China-Philippines-Vietnam disputes), and Arctic (shipping route sovereignty claims). The convention's enforcement gap, no binding mechanism to compel compliance, has been exposed in each theatre.

Article 38 of UNCLOS is the operative clause in the 2026 Hormuz dispute: it guarantees the right of transit passage through straits used for international navigation between one part of the high seas and another, with no toll or prior-authorisation requirement. Iran has never ratified UNCLOS, meaning Article 38 carries no force in Iranian domestic law. The Majlis Hormuz sovereignty law of 2 May 2026 exercises Iranian domestic jurisdiction instead.

The Islamabad Memorandum of Understanding, whose 14-point text was published on 17 June 2026, introduces a new vector: rather than abandoning the toll, the MOU invokes Article 26(2) of UNCLOS to recast the charges as "maritime navigation services" rather than transit tolls. Article 26(2) permits coastal states to charge fees for "specific services rendered" to a ship, a narrow carve-out from the general transit-passage prohibition on fees. Whether the PGSA's flat per-vessel toll qualifies as a "specific service" is legally contested; the plain reading of Article 38 prohibits the charge regardless of its label. Joint management of the strait is assigned to Iran and Oman under the MOU, with Oman's status as a UNCLOS party providing the legal scaffolding: tolls administered through an Oman co-management framework sit partly within UNCLOS-party sovereign jurisdiction rather than as a pure non-party unilateral imposition.

The 60-day charge-free window under the MOU means the Article 26(2) question will re-emerge operationally around mid-August 2026 when the PGSA's renamed charges are due to resume. FM Araghchi confirmed: "charges for services provided will be collected." The Islamabad MOU's OFAC provisions (Provision 3) promised crude-export waivers "immediately upon signing", still unissued three days on, leaving the dollar-clearing exposure unresolved for shipowners who attempt transit under the MOU's fee-for-services framework. The UNCLOS Article 26(2) gambit is the central legal innovation of the post-Ceasefire Hormuz architecture: it accepts UNCLOS's vocabulary while arguing that vocabulary permits the charge.

A second toll question briefly opened and closed in July. On 13 July 2026 President Trump proposed the United States itself levy a 20% toll on Hormuz shipping, before dropping the idea the following day in favour of Gulf States investing billions of dollars in the US in exchange for naval protection. A US-imposed toll would have invited the identical Article 38 objection already levelled at Iran's PGSA charges, extending the transit-passage dispute to a second, non-Iranian claimant; withdrawing it closed that additional front without resolving the underlying Article 26(2) dispute over Iran's own charges.