MASS Regulatory Bridge: Interface Issues between the Legacy IMO Instruments and the MASS Code (MSC.595(111))

MASS Regulatory Bridge is an independent working paper examining the interface between the non-mandatory MASS Code (MSC.595(111), adopted 21 May 2026) and the legacy IMO instruments: COLREG, SOLAS, MARPOL, STCW, and the ISM and ISPS Codes. The paper identifies structural friction points that arise when applying rules written for crewed ships to Maritime Autonomous Surface Ships. Key areas examined include look-out and situational awareness, collision-avoidance decision logic, responsibility allocation across the master, Company, remote operation centre and autonomous navigation system, and environmental obligations under MARPOL. Particular attention is given to the UK Supreme Court judgment in Evergreen Marine (UK) Ltd v Nautical Challenge Ltd [2021] UKSC 6, and to the practical consequences of its holdings on bearing-based engagement of the crossing rules and the “shaping to enter” test at channel entrances. The paper is intended to support the preparation of Concepts of Operations (ConOps), approval bases, and regulatory gap analyses during the voluntary period of the MASS Code (2026–2032). It is not an IMO instrument, not legal advice, and has not been independently peer-reviewed. Primary text and judgment references require final verification against the official instruments.