I did mean IARU and not ITU; for most amateurs the ITU is not approachable and the IARU's function is to bridge that gap and represent the interests of amateurs to the international telecommunications organisations. What I was trying to impart is the current state of confusion which exists with some amateurs who are not so interested or involved at an administrative level.
The example from the UK:-
9(6) When the Licensee operates the Radio Equipment on a Vessel in international waters, use of the radio spectrum shall continue to be made in accordance with Schedule 1, except that the Licensee shall use only those frequency bands which, in accordance with the Radio Regulations, have an allocation to the amateur service in the International Telecommunication Union (ITU) region being visited.
For me, far from being open to interpretation I can see only one; since the ITU Frequency Allocation Table does not include 4m for any of its regions, it must be assumed that 4m operation in international waters is prohibited (for GB Licensees at least).
I think this clearly illustrates the point that 4m is not high enough on the agenda of the international ham community and that a coherent lobby is needed. In the meantime I would probably be wise for anyone considering 4m /mm operation considering entering international waters to seek clarification from their issuing authority?