[font=times]11.4.4 Naval movement restrictions[/font]
[font=times]1. You can’t move naval units between Kiel and the North Sea if an enemy major power controls any of the hexes adjacent to the Kiel Canal.[/font]
[font=times]2. You can’t move naval units between the Eastern Mediterranean and the Red Sea, or between Suez and the Eastern Mediterranean, if a major power you are at war with controls any of the hexes adjacent to the Suez Canal.[/font]
[font=times]3. You can’t move naval units between the Eastern Mediterranean and the Black Sea (even via Panderma) unless Istanbul is friendly controlled.[/font]
[font=times]4. You can’t move naval units between the Baltic Sea and the North Sea (even via Fredrikshavn or Kristiansand) if major powers you are at war with control at least 2 of Oslo, Copenhagen and Kiel.[/font]
I believe that simply if the mentioned cities are controlled by the germans & their aligned, you cannot cross any way to the Baltic by sea, neither directly nor through Frederickshaven. And I don't think it is allowed to leave a ship in the port coming from the North sea and then exit to Baltic the next turn. It would be a prohibition similar to Gibraltar, with the only difference that the port is friendly in this case.
So, the Navals can do a good job but the ships no, unless they were in the Baltic prior to the taking of Copenhagen by the germans, and if ever the british left Frederickshaven they would be doomed, because they would be unable to rebase to a friendly port.