Going dark: legal risks of GPS jamming and AIS spoofing – charterparties

As discussed in Part 1¹ of this briefing mini-series, jamming and spoofing can materially affect a vessel’s navigation and decision‑making. These same issues may also give rise to disputes between owners and charterers, where decisions taken in response to interference impacts the performance of charterparty obligations. In this second instalment of HFW’s briefing mini‑series on the legal risks of GPS jamming and AIS spoofing, we examine the principal areas in which such disputes are likely to arise.

Off-hire

In one case where HFW was instructed by owners, a master exercised reasonable judgment in determining it was not safe to sail, contrary to charterers’ orders, due to jamming and spoofing. An owner would likely assert this constituted a reasonable deviation. Conversely, a time charterer might contend that the vessel was off-hire as the vessel was not performing the service immediately required. Whether or not a charterer’s argument would be successful would depend on the precise wording of the off-hire provisions in the charterparty as well as the exact circumstances of the case.

However, it is possible that a charterer may be able to argue that under the standard NYPE clause 15, the vessel was off-hire for any time lost by virtue of a breakdown of equipment. Whilst there are no case authorities that deal directly with GPS jamming or AIS spoofing, in London Arbitration 23/89, a vessel was unable to return to anchorage due to the condition of its radar and time was lost, with the vessel deemed to be off-hire by virtue of the breakdown of equipment. In theory, a charterer could argue that a vessel unable to sail due to GPS or AIS issues is also off-hire.

The decisive question is whether the GPS interference would qualify as a breakdown. In The Afrapearl [2004] 2 Lloyd’s Rep. 305 (C.A.), the court considered whether a leaking pipe qualified as a breakdown of equipment, holding that “… a breakdown of equipment such as the discharge pipe occurs when it no longer functions as a pipe”. The Afrapearl also refers to The Thanassis A, unreported, March 22, 1982, where the judge in that decision commented that “…The cause of the breakdown is immaterial. It could be some external agent, or it could be some internal defect in the machinery or equipment, but if the machinery or equipment does not function, and possibly also if it malfunctions, then there is a breakdown of the machinery or equipment“. Although fact dependent, where the GPS is being jammed, such that the vessel’s location is not shown at all, it is likely that this would qualify as a breakdown. If the GPS is being spoofed, arguably the GPS receiver is not broken as it is still receiving and displaying GPS signals; it is simply that those GPS signals are false. However, if the spoofed position is clearly false (such as showing the vessel as being on land), then a charterer’s argument that the GPS is malfunctioning would be more convincing. In addition, if an owner has jamming and spoofing resistant technology onboard, and this fails, then a charterer could argue that the breakdown is related to the anti-jamming device, rather than the GPS itself.

An owner may also contend that responsibility for the safety of the vessel and the crew, as well as questions of navigation, ultimately remain with the owner. However, off-hire clauses are typically drafted as no-fault provisions, meaning that a charterer only needs to demonstrate that the circumstances fall within the clause to suspend hire. Further, given that GPS and AIS should not be relied on over visual and radar observations, owners also risk potential criticism for any delays where alternative navigational options were available. In London Arbitration 16/22, a vessel suffered an electrical blackout and could not follow a charterer’s orders for safety reasons. The tribunal held that the vessel was off-hire from the time of the electrical blackout onboard. Consequently, it is unlikely that a court or tribunal would hold an owner exempt from liability where primary sources of navigation remained available.

Unsafe port

Disputes may also arise over whether a port is safe due to jamming or spoofing occurring at the port, particularly in circumstances such as the temporary suspension of vessel navigation ordered by Qatar in October 2025 in response to GPS-related disruptions² (although the same issues may arise at any port affected by GPS interference). In Leeds Shipping v Société Française Bunge [1958] 2 Lloyd’s Rep. 127, the court held that “A port will not be safe unless, in the relevant period of time, the particular ship can reach it, use it and return from it without, in the absence of some abnormal occurrence, being exposed to danger which cannot be avoided by good navigation and seamanship…”.

The first question is likely to be whether the GPS interference is an “abnormal occurrence“. In K/S Penta Shipping A/S v Ethiopian Shipping Lines Corp [1992] 2 Lloyd’s Rep. 545, where a vessel was attacked by rebels after having previously called at the port over 20 times, it was held that the attack was an abnormal occurrence and the port was not unsafe. Where a port is known to suffer from GPS interference, it is likely that the issues will not be held to be abnormal. Another question will be whether the danger could be avoided using good seamanship. In circumstances where it is only the GPS that has issues, with radar and all other navigational aids at the port still operational, it is likely that any danger can be avoided by exercising good seamanship. Further, as confirmed in Kodros Shipping Corp of Monrovia v Empresa Cubana de Fletes [1983] 1 A.C. 736, the concept of safety is not absolute, and where a charterer gives sufficient warning of any GPS issues, it is likely that the port would not be considered unsafe.

Seaworthiness

The classic test for seaworthiness was set out in C. Bradley & Sons v. Federal Steam Navigation (1926) 24 Ll.L.Rep. 446: “The ship must have that degree of fitness which an ordinary careful owner would require his vessel to have at the commencement of her voyage having regard to all the probable circumstances of it.” More specifically, in The Aquacharm [1982] 1 Lloyd’s Rep 7 it was held that “the ship, her crew and her equipment shall be in all respects sound and able to encounter and withstand the ordinary perils of the sea during the contemplated voyage“. It is possible that a charterer and/or cargo interest may argue that a vessel was unseaworthy where an owner was aware of issues with the vessel’s GPS (or potential issues based upon the voyage) and did not exercise due diligence to protect the vessel, perhaps via anti-jamming and/or anti-spoofing software.

The courts have held on several occasions that incompetence of the crew can render a vessel unseaworthy. Such occasions include incompetence when calculating the quantity of bunkers required (The Makedonia [1962] 1 Lloyd’s Rep 316), and inept attempts to fight a fire due to a lack of familiarity with the firefighting system on board and insufficient training for the safe carriage of cars (The Eurasian Dream [2002] 1 Lloyd’s Rep 719). A claimant is also likely to rely on the wide range of international conventions and regulations which govern standards of navigation and seamanship. For example, the International Convention on Standards of Training, Certification and Watchkeeping for Seafarers provides:

If the crew is overly reliant on GPS or AIS, and unable to determine a vessel’s true position using other methods (i.e. manual fixes on known objects or using ECDIS and radar overlays to highlight discrepancies when land is visible either via radar or from the bridge window), a court or tribunal may find a vessel unseaworthy for transiting an area that was well-known for jamming or spoofing incidents, due to crew incompetency. Conversely, if the spoofing was less obvious e.g. displacing the vessel by only 50 metres but still placing her in a shallow area, a tribunal may be less inclined to make a finding of incompetence. In the event that a vessel ran aground as a result of jamming or spoofing, charterers (and/or cargo interests) may seek to defend any claim in general average arising out of the incident (or indeed advance a claim for any losses suffered) by alleging the vessel was unseaworthy. The evidence of the officer on watch and the steps taken to ascertain the true position of the vessel are likely to be pivotal.

Whether a charterer’s arguments in respect of the above areas of dispute are successful will depend on the precise charterparty wording and the specific circumstances of each case.

HFW has seen multiple examples of these disputes arising from both jamming and spoofing. If you require guidance on any of the issues addressed in this briefing, or would like to discuss HFW’s work in this area, please do not hesitate to contact the authors.

Footnotes

1. https://www.hfw.com/insights/going-dark-legal-risks-of-gps-jamming-and-ais-spoofing-collisions-and-groundings/
2. Discussed further in the first briefing in this briefing mini-series: https://www.hfw.com/insights/going-dark-legal-risks-of-gps-jamming-and-ais-spoofing-collisions-and-groundings/