In actuality, it has nothing to do with state law or even US Federal law.  Under the IMO's conventions like STCW and MLC, which all flag states have adopted as law, all ships have a zero tolerance for drug use.  Since there is always some THC in a CBD product (in the US, since the FDA does not regulate it, you are relying on the maker's claims to zero THC), and even countries like Holland that allow certain CBD products (with a specified THC level) do not allow it on their ships.  It is a US Fed