Of course, such a regulation should at least be Europe-wide and apply when the ship is in your harbour (or territorial waters). Taking a detour to refuel elsewh

Of course, such a regulation should at least be Europe-wide and apply when the ship is in your harbour (or territorial waters). Taking a detour to refuel elsewhere takes time. I am unsure how you would check for it, though. Conversely, I have no idea how taxing fuel at the source could ever work, since that source can easily be in countries you have no control over.