Why Has AIS Switch-Off in Hormuz Become a Dispute Issue?

The Automatic Identification System (AIS) continuously broadcasts a vessel’s identity, position, course and speed. In conflict zones, this broadcast can expose the vessel to attack. For this reason, many ships transiting Hormuz in 2026 switched off their AIS for certain periods.

According to Windward, a typical dispute develops as follows: a vessel enters or approaches the Hormuz war risk area and AIS is switched off for a defined window. When AIS is restored, the vessel’s position, cargo condition or operational status appears inconsistent with what the charterers expected. The charterers then allege that unreported ship-to-ship transfers, unscheduled port calls or route deviations took place during the dark window.

According to Windward, the question in these disputes is no longer “was AIS switched off?” but “what did the vessel do during the dark window, and is that consistent with the owners’ stated rationale?”

When Is Switching Off AIS Lawful?

The obligation to carry AIS is set out in SOLAS Chapter V. The rules for its operation are contained in the guidelines adopted by IMO Resolution A.1106(29). Under paragraph 22 of the guidelines:

• AIS should always be in operation when ships are underway or at anchor.
• If the master believes that the continual operation of AIS might compromise the safety or security of the ship, or where security incidents are imminent, AIS may be switched off.
• Such actions should always be recorded in the ship’s logbook together with the reason.
• AIS should be restarted as soon as the source of danger has disappeared.

What Does the BIMCO AIS Switch Off Clause Provide?

To address these issues at contractual level, BIMCO published an AIS Switch Off Clause for time and voyage charterparties in 2021. According to Windward, the clause contains an undertaking that AIS has not been switched off contrary to IMO guidance.

The effect of this clause on disputes is significant: the centre of gravity of the dispute shifts from whether AIS was switched off to proving what happened during the dark period. In a contract containing the clause, documenting a switch-off consistent with IMO guidance becomes the owners’ burden.

How Can What the Vessel Did During the Dark Period Be Proved?

The vessel’s movements can be reconstructed even while AIS is off. Windward lists the sources used for this purpose as follows:

Onboard records should be added to these sources: the logbook, voyage data recorder (VDR) data, engine and fuel records, and the master’s correspondence with the company. In a dispute heard in Turkey, such data can be brought into the file through preservation of evidence (delil tespiti) and expert examination.

What Are the Consequences of GPS Jamming and Spoofing?

In conflict zones, vessels’ positioning systems may be jammed or subjected to false position signals (spoofing). In that case, a vessel may appear to be somewhere it is not, even with AIS switched on.

• War risks and safe port: Interference with positioning systems may bring war risks clauses and the safe port warranty into play.
• Appearance of deviation: False position data may make the vessel appear to have changed route or deviated without authority. This may lead both to a dispute with charterers and to sanctions compliance reviews.
• Documentation: Jamming or spoofing incidents should be entered in the logbook and in reports to the company, together with their time and effect.

Does Paying for Hormuz Passage Create Sanctions Risk?

Reports during the conflict that Iran was demanding payment for passage through the Strait have created a new legal risk for owners and charterers. According to NorthStandard, passage payments to Iran, the IRGC or sanctioned persons carry significant sanctions exposure regardless of the payment method or intermediaries used.

• United States: NorthStandard draws attention to FAQ 1249 issued by the US Treasury’s Office of Foreign Assets Control (OFAC) on 28 April 2026. According to the FAQ, foreign persons dealing with designated Iranian entities may also face sanctions exposure.
• United Kingdom: The Iran (Sanctions) Regulations 2023.
• European Union: According to NorthStandard, the EU designated the IRGC as a terrorist organisation in January 2026.
• Other parties in the chain: The fact that the payment is made by another party in the contractual chain, such as charterers or sub-charterers, does not remove the risk for the other parties.

What do sanctions clauses say in this situation?

Industry-standard clauses such as BIMCO’s Sanctions Clause for Time Charter Parties 2020 prohibit charterers from giving orders involving a sanctioned party or activity. An order requiring a passage payment to the IRGC may fall within this scope.

Can Owners Refuse an Order on the Ground of Sanctions Risk?

In Tonzip Maritime v 2 Rivers (The Catalan Sea) [2026] EWCA Civ 641, the English Court of Appeal gave an important answer to this question. The ExxonMobil VOY2005 form had been used, and the sanctions clause in the contract gave owners the right to refuse an order where compliance would expose them to a real risk of sanctions liability.

The Court of Appeal allowed the owners’ appeal. According to the decision:

• To refuse the order, owners do not need to prove that a sanctions breach would probably occur.
• A reasonable assessment of a real risk of sanctions is sufficient.
• The clause was held to require owners to make a prospective assessment of the effect of future compliance with the order. The Court also took into account the uncertainty and difficulties owners face when deciding quickly.

Do US and EU Sanctions Affect Turkish Shipping Companies?

Unilateral US and EU sanctions are not automatically binding under Turkish law. However, they affect Turkish owners, charterers and agents in practice through many channels:

• Banking: US dollar payments and correspondent banks may block transactions carrying sanctions risk.
• Insurance: Most P&I clubs and war risks insurers are based in the UK or the EU; a sanctions breach may remove cover.
• Contracts: Sanctions clauses in charterparties governed by English law also have contractual consequences for Turkish parties.
• Secondary sanctions risk: US measures directed at foreign persons may also target companies with no US nexus.

Turkish companies should therefore carry out a sanctions compliance review for Hormuz-related transactions, regardless of the law applicable to the contract.

Checklist for Owners and Charterers

Frequently Asked Questions

Can the master switch off AIS?

Yes. Under IMO Resolution A.1106(29), the master may switch off AIS if its operation might compromise the safety or security of the ship or if security incidents are imminent. The action must be recorded in the logbook with its reason and AIS must be restarted once the danger has passed.

Is switching off AIS a sanctions breach?

Not in itself. However, dealings with sanctioned parties or activities such as ship-to-ship transfers during the switch-off create sanctions risk. Documenting the dark period is therefore important.

What is the BIMCO AIS Switch Off Clause?

It is a charter clause published by BIMCO in 2021, containing an undertaking that AIS has not been switched off contrary to IMO guidance. It shifts the focus of disputes to proving what happened during the dark period.

How can it be proved what the vessel did while AIS was off?

Satellite radar and optical imagery, radio frequency detection and behavioural analysis can be used together with the logbook and VDR data.

Is it lawful to pay Iran a passage fee for the Strait?

According to NorthStandard, payments to Iran, the IRGC or sanctioned persons carry significant sanctions exposure, and the risk is not removed by another party in the chain making the payment.

Can owners refuse charterers’ orders because of sanctions risk?

It depends on the wording of the clause. In Tonzip v 2 Rivers [2026] EWCA Civ 641, a reasonable assessment of a real risk of sanctions was held sufficient to justify refusal.

Are US sanctions binding on Turkish companies?

They are not automatically binding under Turkish law. However, they affect Turkish companies in practice through banking, insurance, contracts governed by English law and secondary sanctions risk.

Who is responsible for a route deviation caused by GPS jamming?

It depends on the contract and the documentation of the incident. Jamming may bring war risks clauses and the safe port warranty into play; recording the incident in the logbook and reports is critical for the defence.

Why Is Specialist Legal Support Necessary?

Switching off AIS in Hormuz, interference with position signals and sanctions risk may give rise to contractual, administrative and even criminal consequences within a single voyage. A decision taken by the master at that moment will be assessed months later, in a dispute with charterers, an insurer’s coverage review or a sanctions investigation, on the basis of logbook entries and correspondence. Keeping these records properly from the outset and basing decisions on legal grounds is the foundation of any later defence.

2M Hukuk Law Firm, based in Tuzla, Istanbul, advises shipowners, operators, charterers and agents in Istanbul and Kocaeli on maritime law. We work on the review of AIS and sanctions clauses in charterparties, the drafting of refusal and notice correspondence, evidence strategy in dark period disputes and the handling of charter disputes.

If your vessel is about to transit Hormuz, if you have received a demand for passage payment, or if you are in a dispute with charterers over AIS records, you can request a consultation through our contact page together with your documents.