Who makes the rules?  The classification society, that underwrites the ship.  Both the flag state, and the various insurance clubs (hull, P&I, etc) determine which classification societies meet their requirements, and therefore to fly that nation's flag, or to be a member of the insurance club (most are mutual associations), you have to be classed by that society, and therefore, meet their rules.  As the flag state is involved, this becomes statutory.     This is not some random nu