Under international law all countries are entitled to maintain a maritime fleet. This includes landlocked countries, i.e. countries without a coast line. Therefore it is possible to register an ocean-going vessel in, for instance, Switzerland. Obviously such ships depend completely on foreign ports.
There is no reason that Space Settlements wouldn’t be allowed to maintain a maritime fleet. Theoretically it would be entirely legal for Space Settlements to open a ship register for terrestrial ships. However, space settlements serving as flag states could be a potential source of controversy. Continue reading Flag states