Key takeaways
MASS Code
Currently non-mandatory but mandatory regulation expected in January 2032.
Scope of MASS Code
Covers functional requirements but does not address liability.
Significance of MASS Code
First international regulatory framework for autonomous shipping.
On 22 May 2026, at its 111th session (MSC 111) in London, the Maritime Safety Committee of the International Maritime Organisation (IMO) adopted the long anticipated International Code of Safety for Maritime Autonomous Ships (MASS Code).
The MASS Code, which applies to cargo ships covered under SOLAS Chapter 1, is the first international framework to govern the safe operation of autonomous and remotely operated commercial vessels. It is intended to support the safe integration of AI-enabled and remotely operated commercial ships into global shipping.
The MASS Code is a significant development because it reflects an important shift in autonomous shipping, from limited national trials and regional initiatives toward a more harmonised international regulatory framework.
The Mass Code came into force on 1 July 2026 and applies to cargo ships covered under SOLAS Chapter 1. While the MASS Code is initially non mandatory, the IMO has set out a roadmap for transitioning toward mandatory rules over the coming years, shaped by an Experience-Building Phase, which allows Member States to test the Code in preparation for future mandatory regulation under the SOLAS Convention.
The IMO’s published roadmap anticipates work commencing on a mandatory MASS Code in 2028, with formal adoption by July 2030, and entry into force on 1 January 2032.
The UK Government has responded very positively to the adoption of the MASS Code and has indicated that the UK Maritime and Coastguard Agency (MCA) took a leading role at the IMO drafting stage, in order to uphold UK interests.
The UK Government believes that the MASS Code paves the way to strengthening regulatory confidence for the UK maritime industry by providing clearer, stronger standards supporting technology, innovation and safety at sea.
The UK Maritime Innovation Hub has been designated to answer any questions about how the MASS Code applies to innovative technology in the UK.
Maritime Autonomous Surface Ship (MASS)
The IMO uses the term Maritime Autonomous Surface Ship (MASS) to describe vessels capable of operating with varying levels of independence from direct human interaction, ranging from decision-support automation with crew onboard through to fully autonomous decision-making.
For regulatory purposes, the IMO establishes four levels of autonomy:
ships with automated processes and decision support, i.e., seafarers on board to operate and control shipboard systems and functions, with some operations being automated
remotely controlled ships with seafarers on board, who are available to take control and to operate the shipboard systems and functions
remotely controlled ships without seafarers on board, and
fully autonomous ships capable of making decisions independently.
These distinctions affect how industry and regulators approach core legal and operational concepts in mixed-traffic environments where autonomous and conventional vessels must co-exist.
Scope of MASS Code
The MASS Code is framed as a goal-based instrument aimed at ensuring MASS can be built, operated and certified to safety and environmental standards equivalent to those applied to conventional ships, while addressing functions that may not be fully covered by existing IMO instruments.
The MSC materials describe the Code as supplementary to other IMO instruments (including SOLAS) and as providing a regulatory framework for remote controlled and autonomous operation of key functions.
The MASS Code introduces new requirements for the design, approval and operation of MASS. It emphasises risk assessment, robust system design, cybersecurity and the integration of Remote Operations Centres (ROCs).
The Code comprises three parts, together with an appendix:
Part 1: High-level purpose, principles and objectives.
Part 2: Principles applicable to all cases with resulting provisions met through certification including surveys and certification, software, security, manning, training and watchkeeping.
Part 3: Goals and functional requirements based on modes of operation and functionality including navigation, remote operations, fire management, cargoes, and search and rescue.
Appendix: Forms for certificates and records for autonomous and remote operations.
Issues arising
Importantly, the MASS Code does not address or allocate liability, which means that legal issues surrounding autonomous shipping remain to be addressed by other maritime liability regimes.
This raises a number of legal questions for the shipping industry in terms of risk allocation, which go beyond the scope of this article. However, it is worth highlighting a few matters below.
Accountability in remote / autonomous operations
Since 2017, when the IMO initiated its regulatory scoping exercise on MASS, 2021, concerns have been raised within the global maritime industry in relation to the identity and role of the Master and the division of responsibility between onboard personnel (if any) and shoreside teams.
Stakeholders, particularly from the legal maritime sector, argued that there should be a human Master responsible for each MASS (even where that master is not physically onboard) as human intervention capability remains central.
In response to these concerns, the MASS Code highlights the importance of human oversight, with the Master retaining overall responsibility for the ship at all times – even if not on board the ship.
However, existing maritime liability conventions operate on the basis that a human master and human crew members are performing on-board functions, and the Master is in command. Even remote human oversight leaves many liability questions unanswered.
These unanswered questions may be addressed at the contractual drafting stage, if the shipping industry starts allocating risk in an autonomous shipping context in charterparties, bills of lading and other shipping contracts.
Liability, evidence and causation in a software-driven environment
Autonomous decision-making raises questions about how established legal concepts, including responsibility and fault-based notions, apply when decisions are generated by systems rather than onboard humans.
Traditional methods of collecting evidence, such as interviewing the master and crew, will be overtaken by data capture, retention, and audit trails, particularly where remote operators, connectivity interruptions, or automated decision logic may become relevant to casualty investigations and coverage positions.
The liability net may also be spread much wider than previously. There is potential for liability to extend beyond owners/operators/charterers / etc for casualties to ROC operators, software developers etc. This makes collating and preserving all evidence generated by autonomous systems crucial.
Remote Operations Centres (ROCs), competence and training
In its scoping exercise, the IMO identified the need to clarify functional and operational requirements for remote-control stations / centres and the responsibilities of remote operators as a high priority.
For the reasons mentioned above, there is clear scope for ROC operators to be at risk of liability for casualties.
The MASS Code’s references to manning, training, watchkeeping and remote operations underline that regulators will expect robust governance, competence frameworks and operational procedures that deliver safety equivalence with conventional shipping.
Search and rescue (SAR)
The International Maritime Rescue Federation (IMRF) has raised concerns that the SAR Chapter in the MASS Code leaves important technical questions unanswered in relation to how MASS will safely and effectively conduct rescue operations involving persons in distress. It is also unclear how and where a MASS will accommodate rescued survivors.
The IMRF notes there is a technical challenge to replicating human functions for rescuing people at sea. Additionally, there may be operational issues for SAR units to work with MASS that are remotely controlled from shore-based ROCs.
On the other hand, MASS may be fitted with high-level sensors that enable them to better detect objects or persons in the water. As a result, a MASS may be valuable during SAR operations.
Cybersecurity and connectivity as ’core safety’
The MASS Code’s inclusion of connectivity and remote operations reflects that cyber resilience and communications integrity are becoming operational safety issues, not merely IT considerations. IMO guidance on MASS workstreams also points to the importance of cyber risk management as autonomy increases and reliance on shoreside control grows.
Checks for cyber risk compliance within safety management systems have become standard for port state control inspections. Proof of satisfactory cyber defence systems may also be a prerequisite for obtaining insurance cover.
Wider application to other vessels
Whilst the current MASS Code is limited to cargo ships as defined under SOLAS, there is also the question around its extension to other autonomous and non-commercial maritime vessels.
Whilst such extension will no doubt take some time to reach implementation and will be shaped by the experiences gained following application of the MASS Code, it is ultimately inevitable, when further questions will arise.
Conclusion
As with all non-mandatory regulation, the impact and reach of the MASS Code will depend on how quickly and the extent to which it is adopted by Member States.
There may also be some divergence between the MASS Code and domestic regulation of MASS as well as in the way different Member States interpret and apply the MASS Code.
Nonetheless, the non-mandatory Experience-Building Phase allows stakeholders to address potential obstacles to an effective and mandatory regulatory framework when it is in due course enacted.
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This article was authored with the assistance of Trainee, Josh Evans.
